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The Haynes

Welding
Manual
by Jay Storer
and John H Haynes
Member of the Guild of Motoring Writers

The Haynes Manual
for selecting and using welding equipment
ABCDE
FGHU
KLMNO
PQRS

Haynes Publishing Group
Sparkford Nr Yeovil
Somerset BA22 7JJ England
Haynes North America, Inc
861 Lawrence Drive
Newbury Park
California 91320 USA

Haynes Welding Manual

Acknowledgements
We are grateful for the help and cooperation of welding equipment
manufacturers such as Airco, Daytona MIG, HTP America, Lincoln
Electric, Miller Electric and the ESAB Group, for their assistance with
technical information and illustrations. Thanks to FitzMaurice-Smith
Racing in Ventura for assistance with cover photography. We also
wish to thank the Eastwood Company, Maguire's Welding and Valley
Vintage Rods for assistance.
© Haynes North America, Inc. 1994
With permission from J.H. Haynes & Co. Ltd.

A book in the Haynes Automotive Repair Manual Series
Printed in the U.S.A.
All rights reserved. No part of this book may be reproduced or transmitted in any
form or by any means, electronic or mechanical, including photocopying, recording
or by any information storage or retrieval system, without permission in writing
from the copyright holder.

ISBN 1 56392110 3
Library of Congress Catalog Card Number 94-74485
While every attempt is made to ensure that the information in this manual is correct, no liability can be accepted by the authors or publishers for loss, damage or
injury caused by any errors in, or omissions from, the information given.
94-176

Contents
Chapter 1

Introduction

Definition of welding
Development of modern welding
Welding today

Chapter 2

Types of welding

How it works
Metal alloys
Oxy-acetylene gas welding
Arc welding
MIG (wire-fed) welding
TIG (heli-arc) welding
Duty-cycles
Plasma-arc welding and cutting
Practice and training

Chapter 3

2-3
2-3
2-6
2-9
2-11
2-14
2-17
2-18
2-21

Oxy-acetylene gas welding/cutting

The basic gas process
The equipment
Getting started
Flame adjustment
Gas welding
Welding with filler rod
Brazing
Oxy-acetylene cutting
Heating with oxy-acetylene

Chapter 4

1-2
1-3
1-6

3-1
3-3
3-7
3-9
3-9
3-11
3-16
3-18
3-24

Arc welding

Comparing duty-cycles
AC, DC or both?
Rewiring for an arc welder
The arc process
Safety considerations
Beginning arc welding
Types of joints
Choosing electrodes

4-3
4-4
4-5
4-6
4-7
4-8
4-11
4-13

Haynes Welding Manual
Chapter 5

MIG welding

Shopping for a MIG welder
Choosing shielding gas
Choosing wire
Learning MIG welding

5-5
5-12
5-14
5-16

Chapter 6 TIG welding
The equipment
The process in action
TIG-welding aluminum

Chapter 7

6-4
6-8
6-13

Plasma cutting/welding

Plasma-arc welding
Plasma-arc cutting
Choosing plasma cutting equipment
Using a plasma cutter

7-2
7-3
7-5
7-8

Chapter 8

Safety and shop equipment

s1

Chapter 9

Building a utility trailer

9-1

Glossary
Sourcelist
Index

QL-I
sn
IND-1

Introduction
Welding is a process critical to our present state of civilization and technical
advancement, yet little understood and most often taken for granted. Unless exposed to the building, machinery or automotive trades, the average person never
realizes how much we depend on the welding process, which is a fundamental
part of the process of building most of what we depend on daily, including vehicles, buildings, appliances, bridges and a great deal
more. In fact, once you really start to examine the objects around
us, it's hard to imagine our world without the welding process.
Architecturally speaking, we might all be living in one-room
wood or adobe-brick houses if it weren't for welding. Certainly all
large commercial and residential structures are built with a considerable "skeleton" of welded structural steel, and even most singlefamily, wood-framed houses are built using some welded components, even down to items like the electrical outlet boxes in the
walls. Anyone who has watched the construction progress of a major highway improvement like a bridge or tunnel has seen the helmeted weldors, unsung heroes of the construction process, spraying a shower of sparks from high on a scaffold while they join
metals to hold critical loads.
Sitting in an airport terminal recently with some time on our
hands gave us something to think about. Virtually everything
around us involved welding in some way. There was a large rack of
telephone books in stainless-steel racks, each carefully TIG-welded
and sanded, a post office box that was made of welded steel, the
telephone stall had welded components, and the seats we were sitting on were part of a welded-steel structure that held eight seats.
Everywhere you look in the modern world, you'll find examples of
how widespread and important is the use of welding techniques
and equipment.
Much of our Haynes audience is familiar with the automotive
world, and here is a field where construction and repairs made by
welding are absolutely essential, in fact essential to virtually all
1.1 Welding had its ancient origins in the fires of
blacksmiths, who could forge two white-hot pieces of
forms of transportation, from bicycles to cars, trucks, trains, aircraft
metal together with hammer blows and patience. It
and space vehicles. Even if we could go back before the "horseless
remained for history to bring us to electricity and
carriage" was developed at the end of the 19th century, we would
bottled gasses for welding techniques to develop any
still need some form of welding to return to horse-drawn transfurther. Modern-day farrier (blacksmith/horseshoer)
portation, in welded brackets for harnesses and wagon compoRichard Heller illustrates the old ways.
nents.
1-1

Haynes Welding Manual

1.3 The farrier of today works out of a truck, filled with equipment like
a grinder, drill press and welder, all running on AC power when
available; otherwise, horseshoes are shaped in a portable forge.
Today's blacksmith has the advantage of tools like this MIG welder
that speed up making special horseshoes.

1.2 Metal cutting in the old days was no easier. A
white-hot piece of metal was laid over a hardy (like a
wedge or chisel point) in the big anvil, and struck
hard with a hammer, chopping the softened piece
off. Final shaping of most items was by hand with
stones and files.

Since we've established that welding is a technical process our
present society can't live without, in this book we'll explore more
about the process, removing the mystery, and examining the available equipment as it can be useful to us in fabricating with metal or
repairing metal items. We'll show all of the most up-to-date equipment, describe the various welding types, make recommendations,
show how welding is used in everyday situations, and develop welding projects that illustrate how you can build or repair automotive,
farm and household objects.

Definitions of
welding

1.4 Under the center bridge column here are a welder (a machine) and a
weldor (a person). He is welding up steel enclosures for the concrete
columns, to retrofit more strength in California bridges to meet newer
earthquake codes.

1-2

At one time, the simple definition of welding
was "joining metals through heating them to a
molten state and fusing them together." As technical progress in welding processes has advanced, the definition has had to change.
There are now two basic forms of welding:
fusion and non-fusion. The former is the most
common, and it involves the actual melting of
the parent metals being joined. Not all welding
today involves melting. Non-fusion welding is
most commonly represented by soldering and
brazing, two processes of joining metals where
the parent metal is heated, but not melted, and a
second or "filler" metal is melted between them,
forming a strong bond when all are cooled.
Pressure and friction alone can weld metals
together, such as when a machinist turns down
a piece of metal in a lathe. Often, pieces of the
metal chips can become welded to the cutting

Introduction

1.5 Wherever you see buildings go up, the basis for them is always
steel, whether they wind up with wood, bricks or
cement on the outside, it all began with the work of
ironworkers and weldors.

tool, which is a simple example of a process that can be used in
1.6 The construction and repair of heavy equipment
production work in joining metals. Other kinds of "cold" welding
and farm machinery would be nearly impossible without
may today involve sound and light, as in sonic-welding or laserwelding. Arc welding is usually used, as here modifying
welding.
the front of a dirt scoop on a John Deere, where
Today, the term "welding" has even been applied to the
welding is outdoors and on heavy plates.
processes of joining non-metallic materials, such as plastic-welding which sometimes involves a fusion of materials as a result of
heat or chemical action. As kids, we have all played with plastic models that we
constructed using "glues" that would react with and actually "melt together" the
two pieces we were joining.
For today's definition of welding to be all-encompassing, it would have to
read "the joining of metals and plastics without the use of fasteners." This definition covers a lot of ground, but, given the interests and needs of the majority of
our readers, this book will concentrate on welding as it applies to metals joined
by heat processes produced either by a flame or electrical current.
Semantically speaking, throughout this book we will be illustrating and referring to pieces of welding equipment and to the people who operate them. Sometimes the same term "welder" is used to apply to both the machine and the man,
which can become confusing, so for our purposes, we will from now on refer to
the machine as a "welder" and to the person operating it as a "weldor."

Development of
modern welding
Welding can trace its roots far back in time to the first blacksmiths who
heated and shaped metals. At that time, metals were primarily used for tools and
weapons, both of vital importance in those days. The blacksmith was an important tradesman in any community, earning a little more respect than most, even
by lords and kings who depended on weapons for maintaining power. The "art"
of smithing was understood by a select few, and blacksmiths were accorded almost the fear-based respect of a low-level sorcerer. Given the traditional image
1-3

Haynes Welding Manual

1.7 Welding is even used in many art forms today.
Bill McKewen is a metal sculptor who works with
rods, tubes, plates, wires and custom castings to
create interesting works that combine hard metals
with "organic" elements.

1.8 One of Bill's largest works is this 30-foot tall sculpture called
"Organic Form 1", which is made entirely of stainless-steel and weighs
over 1000 pounds.

1.9 In a close-up of the "transition
point" in Bill's sculpture, we can see
how the stainless tubing and solid rod
is wrapped with stainless-steel oil
field cable and welded to a large
shape originally carved of foam and
then sandcast in stainless and finalshaped with a body grinder.

1-4

of the blacksmith as a large, muscular man covered with soot who
works in a fiery, smoky environment, hammering loudly and magically
making useful objects out of nothing, it's no wonder he was treated a
little differently.
The blacksmith heated metals in a wood fire (coal was used later
on) and hammered them into tools and weapons, performed basic
heat-treating to harden some areas, and ground sharp edges with a
foot-powered stone grinding wheel.
There were times when an object couldn't be made from one
piece of metal. Gradually, the techniques developed to join pieces of
metal either with bolts, hot rivets, or welding. This first use of welding consisted
of heating the objects to a certain color (fairly precise indicator of the temperature) and quickly hammering them together on the anvil. The heat and pressure
joined the items, and the process has been called "forge-welding."
As history marched on, larger and larger items had to be made of metal, especially with the industrial revolution of the 19th century. Most machinery was
made of cast metal, produced when molten metal was poured into a mold and

Introduction

1.10 In high-technology areas like nuclear vessels, aviation
and here, at a large race car-building shop, quality welding
technology is critical to success with metals.

1.11 Not every welder and weldor works indoors. This is an
oil field service truck with gas-welding/cutting equipment, arc
welder and crane. Many welding shops have portable setups
like this for remote jobs.

allowed to solidify. Repairing broken castings was a
common procedure in industry and manufacturing.
Cast metal is too brittle for forge-welding on an anvil,
and the items were too large, so a process of "castwelding" was developed in which the broken machinery was heated, a temporary mold bolted around the
area to be repaired, and molten metal was poured in.
Done right, the molten metal bonded with the parent
casting and the goldrush mine or cotton gin was back
in business.
As the 20th century dawned, electricity came into
wider usage, especially for lighting. The early carbonarc lamps made as much heat as they did light, and
someone started using electric carbon-arc rods to fusion-weld metals. Soon after, the simple stick electrode
was developed that is similar to arc-welding rods of today, and about that same time oxy-acetylene gas weld1.12 The back of the same oil field welding truck is built as a
ing was also developing. It's ironic that gas welding
large, heavy workbench-away-from-a-shop. Big Lincoln ac/dc arc
also grew out of the advancements in lighting, since
welder has its own engine power and generator to run lights for
night work.
acetylene gas had been used for car lights up until just
before W.W.I.
Speaking of W.W.I, anyone who is familiar with history knows that many
technological advances have resulted from the accelerated development that,
unfortunately, only seems to come from a wartime environment. W.W.I saw the
further development of gas and stick welding, and soon after that the refinement
of X-ray technology aided further industrial use of welding. The exacting inspection of welds made possible by X-rays speeded welding's acceptance.
The rapid development of the aircraft industry between the wars, and the increased use of lightweight metals to replace wood and fabric in fuselages and
wings led to further advances in welding. W.W.II saw the burgeoning aircraft industry with increased requirements for joining light metals such as aluminum and
magnesium faster, stronger and smoother than with drilling and riveting, as had
been used before. Inert-gas welding was invented before the war, but the gasses
were considered too expensive at the time, and it took a war-time environment to
accelerate its development. After the war, because the lightweight metals were in
demand for many military and civilian applications, TIG welding was further refined, and MIG welding was invented around 1948.

1-5

Haynes Welding Manual

1.13 Back in the Fifties and Sixties, car enthusiast magazines were all
advertising these "twin carbon-arc" welders, which were the original
"Buzzboxes." While some of these did work, most of them were tried a
few times and then put on a shelf out in the garage. Today they're
collector's items from welding history.

1.14 Today's modern home/shop/garage welding
equipment is likely to be a clean, efficient, safer
welding system like MIG, or wire-feed, welding.
Machines like this are getting less expensive all the
time, and some models can be hooked to standard
household 110V current, making them quite portable.

Today
In the remaining decades of the 20th century,
welding developments have come at a rapid pace,
often closely tied to electronics development, as
new and better methods of applying cleaner and
more controlled heat have come along. In the past
decade,
we have seen the cost and complexity of
1.15 If you decide to purchase a welder, visit your local welding
welding equipment reduced in some areas, to the
supply center to talk to the salespeople and find out what equipment
point where equipment that was once considered
best suits your needs and budget. A well-equipped store will have
everything you'll need, from gasses to glasses.
solely the province of the high-production professional shop is now found in garages and hobby
shops around the country.
It's been good news for the automotive hobbyist, whether he is restoring an
old car or building a race car, as well as good news for the small farmer trying to
maintain and repair his equipment. Welders are now being purchased by metalsculptors and other artists and craftsmen, as well as being used for the most
everyday kinds of household jobs such as repairing a bicycle or garden tool,
building a firewood storage rack or a barbecue, or even fabricating a small utility
trailer at home.
Welding has been compared to playing a musical instrument. In the same
way that anyone can pick-up a harmonica and start making sounds with it, most
anyone with some mechanical aptitude can, with a little practice, start using pop1-6

Introduction
ular kinds of modern welding equipment for non-critical jobs. But to make music
with that harmonica, or good, strong, clean welds with a welder, will take time.
As the hip musician once said when asked how to get to Carnegie Hall, "Practice, man, practice!" The more time spent consistently practicing with a welding
setup, whatever the type, the better your results will be. If you use your welder
only occasionally, don't just pick-up the torch and expect to lay a perfect bead
the first time. There is a rhythm to find. Practice first on a scrap piece of metal of
the same thickness as the work you intend to weld, and, when you have the
rhythm down, repair or fabricate your job.
Though not considered with the same awe as the ancient blacksmith, a professional weldor today can still make a satisfying living, for it seems to be a skill
that, far from fading out due to replacement technology, is seeing ever-increasing usage in business and industry. Weldors today find diversified employment in
oil field and pipeline work, building construction, bridges and other infrastructure,
automotive work from assembly-line welding to body shop repair to race car fabrication and antique auto restoration, to the nuclear-power industry, aviation and
aerospace work, defense work, and manufacturing work building products from
household appliances to huge boilers and construction equipment.
This book is intended as an overall introduction to the welding process, illustrating most of the common equipment and work techniques for both home and
shop welding. While this is not a textbook for the would-be professional weldor,
there is enough of an overview here to give a prospective welding student a basic
understanding before delving into the more detailed professional textbooks on
the subject.
Whether you plan to restore a vintage car, build a race car or experimental
aircraft, construct your own wrought-iron fence, sculpt a metal art masterpiece,
or go into welding professionally, you'll find this book of interest. The handy
Source List and Glossary of Terms at the end of the book will be helpful for future
reference.

1-7

Haynes Welding Manual
Notes

1-8

Types of welding
If you are reading this book, chances are you have had some exposure to
welding through watching a repair done such as having a new exhaust system
put on your car, through some hobby interest in the metal arts/crafts area or
through some industrial exposure to welding as used in manufacturing and
building processes. Obviously you have become interested enough in learning
about welding to purchase this book which we feel is an excellent introduction to
a field where there are lots of involved textbooks for the person pursuing welding
as a profession, but few basic books for someone getting started at the hobby,
farm or home/shop level.
Perhaps your initial exposure to welding has sparked an interest in doing it
yourself. If you are involved in automotive work, you already know how
valuable the process can be in fabrication and repairs. Once you have
seen it performed, you realize how
handy this capability is. You can join
pieces of metal to either repair something that was damaged and otherwise scheduled for replacement or
build something entirely new, from a
barbecue grille to a race car.
Once you have the basic skills
and the right equipment, you'll find
many more uses for welding than you
had anticipated. Like a good truck or
a specialized tool, once you have a
welder, you'll wonder how you ever
got along without it! You'll probably
find yourself building a materials rack,
stocking it with various sizes of tubing
and plates, and actually looking for
new projects to tackle, from building a
workbench to last a lifetime, to storage racks, moveable shop carts, engine stands, shelving, and much
more.
There are quite a few types of
2.1 There are a number of choices today when shopping for welding equipment.
welding processes, and today there
The right choice for you depends on the kind of jobs you plan to do, where you plan
are a great many welders to choose
to do them, your budget and how much time you can devote to training and practice
from. There are so many, in fact, that
before you become proficient at one of the methods we'll be looking at.
just picking the process and the ma-

2-1

Haynes Welding Manual

2.2 Welding is a process of fusion, in which metal parts are heated to the melting point and fused together, usually with a filler of
the same material melted along with the "parent" metal. All metals melt at different temperatures, and this chart shows some
interesting comparisons, as well as relating the heated metal's color to its temperature.

chinery which best suit your needs may seem a considerable task. This chapter
will give you a brief overview of the various processes along with an analysis of
the pros and cons for each type and how best to select equipment based on your
needs.

How it works
The most basic principle of the welding process is joining two pieces of
metal together (or at least two edges of the same piece, in the case of repairing a
crack). This is generally accomplished by heating the metals to be joined until
they become liquid or molten and the two edges fuse together. Most often, the
complete joining of the two metal edges is accomplished by melting new metal
into the joint at the same time. The new metal added to form a fused welding joint
is called filler metal, while the original pieces being joined are called the parent
metal. Together they form a welded "bead" of filler and parent metal that is usually thicker than the parent metal. Depending on the skill of the weldor and the
type of welding, two pieces of metal can be joined in such a way that with a little
filing or sanding of the bead, the joint is virtually undetectable, a particularly important aspect when making automotive body repairs. The first time you may
have observed a professional weldor working, the process may have seemed like
a sorcerer doing alchemy with a magic wand. With the proper equipment and
practice, you can do a little magic yourself, a magic that can give tremendous
personal satisfaction, as well as save you considerable expense compared to
having the same work done at a professional fabrication shop.
2-2

Types of welding

2.3 The welding corner of this well-equipped race-car prep
shop holds a variety of equipment, from a large TIG machine
at left (with cooling unit on top), to a heavy-duty plasma
cutter, oxy-acetylene cutting/heating/welding outfit, and two
small plasma cutters. Not shown here are the two MIG
welders in use elsewhere in the shop.

It takes a tremendous amount of localized heat to weld metals together, and
heat control is the key to welding properly. Every material has its own specific
melting point, and to make a weld you need to heat the material to that point but
not beyond it. Visualize an ice cube, which is solid material (when cold). If you
heat it to the melting point (above 32 degrees F), the solid becomes a liquid (water), heating it further will vaporize it into steam and for your purposes the material is gone. The same changes happen to metal, although at much higher temperatures. Common lead solder such as you might use to solder electrical
connections can melt at temperatures from 250-750° F (depending on the alloy),
aluminum melts at just below 1250° F, and common mild steel melts at 2750° F.
The heat required to make metal molten enough to fusion-weld can be
achieved in several ways, but the most common for home/shop situations will
be generated either with a flame or some use of electrical current. The traditional
source in welding has been the oxy-acetylene torch, while electricity is now
used in most of the other methods, such as arc-welding, MIG-welding, and TIGwelding.
One thing that is common to all the forms of welding is that the filler material
must be compatible with the parent metal, and all efforts must be made to make
a "clean" weld free of outside contaminants that could weaken the joint. If you
are welding aluminum, the filler rod must be aluminum, a stainless filler rod must
be used for welding stainless-steel and steel rods are used on steel. In gas
welding, the cleanliness of the weld is controlled by the correct adjustment of
the torch flame and the cleanliness of the two edges of the parent metal. In electric welding, an inert gas "cloud" is formed right around the welding area that
keeps outside oxygen or impurities from contaminating the weld. The shielding
gas is generated in several ways, as you'll see as we further describe the various
types of equipment.

2.4 You will have to develop some
new contacts once you get into
welding, one of which will be a reliable
local source for metals for your
projects. This is ABC Metals
(aluminum, brass and copper) in
Oxnard, California. They have a lot of
aluminum here at scrap prices, but it's
more of a gold mine for the hobbyist
or car-builder who needs relatively
small bits and pieces and not a
trainload. Knowledgeable salespeople
at a metal yard can be very helpful.

Metal alloys
The melting point of the metal you work with will vary with the basic nature
of the material (iron, steel, aluminum, magnesium, etc.), and the alloy of the
metal. Most metals today are not in pure form, they are alloyed or mixed with
another metal to give the new material special characteristics. Copper, lead and
iron are basic pure metals that have been used by man for tools and other ob2-3

Haynes Welding Manual

2.5 Non-ferrous metals like aluminum are generally
marked with their alloy and heat-treat, such as here on
this sheet of 6061-T6. If you need a specific metal for a
project, you may have to buy new material rather than
remnants, because the smaller scrap pieces may not
have the markings on them.

2.6 Weldor Bill Maguire fabricated this recumbent bicycle for himself
from 4130 chrome-moly thinwall tubing, which is very strong but
light. The idea was to reduce the bike weight, wind resistance and
pedal effort. Bill joined the thin tubing with TIG welding.

jects for thousands of years. Mixing various metals together can produce a new
metal with new uses. Copper mixed with zinc will make brass, which has
strength, reduced cost, and better suitability for machining and casting. The
same base copper mixed with tin makes bronze, which was alloyed as far back
as 2000 years to make weapons. Gold and silver, precious as they are in their
pure state are seldom utilized in their natural form which is quite soft in comparison to other metals.
When alloyed with other metals which add strength or other characteristics,
gold and silver can be used for jewelry, coins and many other uses. We commonly describe different gold objects by "carats." While pure gold is 24 carat,
12-carat gold is only half gold and half other metals, and the closer the caratnumber is to 24, the more gold is in the object. The other alloys reduce the expense of the pure gold and make it more durable and useful. Were rings and
other jewelry to be made of 24-carat pure gold, they would be too soft and not
last in normal use.
Most of the metals you will be working with in your welding will be of two
kinds, ferrous and non-ferrous. The former includes metals that contain iron,
most commonly steel. The most commonly-welded non-ferrous metal is aluminum. Both steel and aluminum can vary considerably in the welding process
depending on the alloy. By changing the alloy of either steel or aluminum, different properties can be obtained, to either make the metal more flexible (ability to
bend without breaking), malleable (ability to be formed with a hammer), ductile
(ability to be drawn out or hammered thin) or to improve its strength for a specific
application. Steel is made from refined iron combined with carbon and other elements. How much carbon is added determines the properties of the steel alloy.
Most of the steel we might use for projects is relatively low in carbon, called mild
steel. With higher levels of carbon, you get medium-carbon steel (used for shafts
and axles), high-carbon steel (used for automotive and industrial springs), while
very-high-carbon steel is used to make files and sharp-edged cutting tools. The
common mild steel we use most often is weldable by virtually all of the techniques described in this book, while the higher-carbon steels have special requirements. Other elements commonly alloyed with steel are manganese, tungsten, nickel and chromium. The latter two combine with steel to make
2-4

Types of welding

2.7 Get to know the personnel at your local welding supply
store. They can be very helpful when it comes to choosing
equipment, and they will have all the supplies you'll need in
the future. Most stores carry several brands of equipment, all
the safety items, and even the smaller home/shop machines.

2.8 The welding supply store should be able to tell you where
to buy steel locally, which you will probably use for most of
your welding projects. Most yards have a remnant section as
shown, where you can buy short lengths of material at by-thepound prices. Tubing for a trailer project is being weighed.

stainless-steel, a very useful material that requires somewhat different welding
techniques. Anyone familiar with race-car and aircraft construction may have
heard of 4130 chrome-moly steel, which is often used in these applications for its
high strength relative to its weight. The four-digit number describes the alloy as
containing molybdenum, and the amount of carbon. This alloy contains more
carbon than mild steel, as well as chromium and molybdenum, both of which add
properties of rust-resistance, strength and hardness. Even though this is a
higher-carbon steel than mild steel, it really contains only 30/100th of 1% of carbon, which shows how scientific the alloying of metals really is. A tiny change in
content can radically affect the properties of the final metal.
In steel and aluminum, not only are there different alloys, but different heattreat processes. In the simplest terms, heat-treating is a scientific process of
heating a metal to a specific temperature and then cooling it, either slowly or
quickly, and with or without oil. The heat-treating can affect the hardness and
other characteristics of the metal. When aluminum is purchased new in sheets or
tubes, it is generally marked with its alloy and heat-treat, such as 3003-T3, which
is a sheet aluminum that is considered "half-hard" and is commonly used in making race-car bodywork, where it has to be somewhat strong, but also able to be
bent, welded and hammered. On the other end of the spectrum, 7075-T6 aluminum is very hard and strong. Called "aerospace aluminum" in the vernacular, it
is often used in making machined aluminum parts and applications where very
high strength is required. While it is strong and hard, it doesn't bend. There are
volumes of scientific books on the alloying and heat-treating of metals, but, for
your purposes as a home weldor, just remember to find out what kind of metal
you are welding, and when making a project ask a metals expert to recommend
the most suitable material. In general, the higher the carbon content in steel, and
the higher the heat-treat on aluminum, the stronger the material will be but
tougher to form into a shape, and the tougher metal alloys can be more brittle.
If you do decide to purchase a welder, you will eventually get to know the
people at your local source for welding equipment, and they should be of considerable help in answering your questions and getting your setup working well.
They will also be able to tell you where locally to purchase the metals you need
for your projects. Most metal supply houses have a "scraps" section where you
can purchase cut ends, small plates and short lengths of various tubes, all at
about half the price of prime material, which is usually sold in large, unwieldy
2-5

Haynes Welding Manual
sheets or 20-foot lengths of tubing. Use the scrap pieces for all your experimentation with various types of welds, until you are doing pretty well. You may even
be able to build small projects, like a welding cart, using the short lengths of tubing or angle-iron from the scraps section. Once you get to know the people at
both the welding supply house and the metal yard, you'll have experts to wade
through the technical jargon of alloys and heat-treats, and help you sort out the
right material for your future projects.

Oxy-acetylene gas welding
This is perhaps the oldest and most versatile of welding setups. For a long
time, it was the only setup recommended for the home/shop use, and has been
among the least expensive to get started with. The basic combination in a typical
gas-welding package are two high-pressure cylindrical tanks, one for oxygen,
one for acetylene, a set of gauges and regulators to control the gas flow out of
the tanks, a pair of hoses, and a torch. The torch usually comes with a variety of
tips, tip cleaners, a spark lighter, and good sets may include a helmet, gloves
and often a cutting-torch.
The latter is what really makes the oxy-acetylene system so versatile. It is
one of the few welding systems that can do cutting as well as welding. This can
be invaluable in both repair and fabrication work. Cutting away damaged or unwanted material is easily done with a properly-used cutting-torch attachment,
and you may have many projects where you need to cut an irregular shape out of
steel plate. The bulk of tubing and angle-iron cutting is usually done with some
kind of saw or an abrasive cutoff wheel, but these tools can only make a straight
cut; they can't go around corners. If you need to cut out a circle from a steel
plate, you can draw the circle on the plate with a compass and a special hard
crayon called a soapstone (which leaves a line you can see even when welding),
then use your cutting torch to follow the line and you have your part. Any shape
can be cut out. If you make up a cardboard template of the piece you need, trace
around the pattern with your soapstone onto the plate, and make it.
Cutting with a torch takes skill to closely follow a line, and even then the
edges of the metal will require some grinding, filing or sanding to get a smooth
edge. Most experienced weldors know just how much to cut outside their pattern

2.9 Gas welding with oxygen and
acetylene gasses is one of the oldest
forms of welding, and is still used today
in construction, muffler shops and farm
repairs. Its versatility lies in the ability to
cut and weld, on thick and thin materials,
and to do braze-welding as well. The flux
shown is only used for brazing. Note
the different size and shape of the two
gas cylinders.

2-6

Types of welding

2.10 You'll n e e d a s a f e a r e a to p r a c t i c e your g a s w e l d i n g . Fire
bricks like t h e s e a r e s a f e t o w e l d o n a n d d o n ' t s u c k t h e h e a t
out o f your p a r e n t m e t a l a s y o u w e l d . T h e skills you'll h a v e t o
learn w i t h g a s w e l d i n g a r e t o r c h m o v e m e n t , e v e n f e e d i n g o f
filler r o d w i t h your other h a n d , a n d s t e a d y , s m a l l c i r c l e s t o
m a k e consistent puddles.

size to have an exact-size piece after cleaning up the cut edges with a
grinder.
The oxy-acetylene setup is still the least expensive welding system if you
buy the torches, gauges and hoses, and lease the gas cylinders. The tanks
are expensive to purchase outright, but can be leased from your local welding
supply store with a deposit down and a small monthly fee. Many shops today
will take a credit application in lieu of a deposit, and you will open an account
there, assuming your credit is good.

2.11 This illustration shows virtually all of
the basic weld types and positions. With
each type of welding you practice, you'll
first learn to make a steady bead on a
steel plate, then do flat butt-welds, then
move on to corner welds and tougher
ones like overhead and vertical welds. If
you first learn torch control with gas
welding, you'll be able to pick-up any
other welding method more easily.

2.12 Oxy-acetylene torch flames can be put to some sophisticated uses. This is a mechanical gas pattern cutter (ESAB
Silhouette 500), which can follow a pattern under the stylus and cut out two identical copies with the torch heads at right.
Intricate parts can be cut out repeatedly, and with very clean edges because the torch movement is motorized and very smooth.
2-7

Haynes Welding Manual
Leasing tanks is an inexpensive way to get started, but if you do only a small
amount of welding infrequently it may not be a practical arrangement for you. After you have been paying rental fees for a year or two, you'll realize you could
have purchased the tanks outright for the same amount of money. If you knew
you only had to do some gas-welding for a few months, then the leasing deal
would be better.
When welding with oxy-acetylene equipment, the basic procedure is to set
the proper gas flow to the torch with the regulators, crack open the valves on the
torch, light the flame with a friction-sparking lighter and then adjust the ratio of
oxygen to acetylene to achieve the proper flame. Changing tip sizes makes a
bigger or smaller flame, so you suit the tip size to the thickness of the parent
metals you are welding. A smaller flame is used for thinner metals. The torch is
brought down to the work area (the weldor is wearing his dark-lensed safety goggles) and the flame is used to heat the two edges to be joined, while your other
hand feeds a piece of filler rod into the molten puddle as you move along the
joint. Weld joints can be made with or without a filler rod, but a filler rod is used
most often.
This is a very simplistic description of the process of gas-welding. It takes
considerable practice and good hand/eye coordination to master. Once learned,
the skills can be very useful, but it is a process rather difficult to learn from a
book. Taking a class or having an experienced friend take you through the
process will ease the learning curve considerably.
Besides the versatility of doing both welding and cutting, oxy-acetylene
equipment also has many other shop uses in supplying a lot of localized heat.
You may have projects where you need to bend a piece of metal. Thin sheet
metal can be easily bent with pliers, vise-grips or put into a vise and bent over
with a hammer, but thick metal may crack when bent cold. If you have a 1/4-inthick steel bracket you need to bend at an angle, cold-bending with a hammer
and vise may require so much hammer force as to distort the part out of shape,
as well as mark the surface up or even damage the vise. If you closely examine
the piece of thick plate after a cold bend, you may see the metal in the corner of
the bend looking crystallized, which weakens that spot. Heating the metal to the
right temperature with a torch before bending it, along the line where the bend
should be, allows an easy bend with less disturbance of the metal's integrity
along the bend. Another use of gas welding equipment is for brazing ferrous and
non-ferrous metals such as copper and brass. In brazing, the parent metal is not
made molten, it is heated enough to melt a brass filler rod, which attaches to
both pieces of parent metal, making a firm joint.
Besides heating metal for bending, gas equipment is also used in many automotive shops for freeing frozen parts. Metals expand when heated, and when a
rusted nut on a fastener is heated, the nut expands and breaks the bond, so the
nut can be removed. When working under a car that has seen winter road salts,
or when disassembling an old car for restoration, a gas torch can be very handy
for getting off rusted nuts without busting your knuckles when your wrench
rounds off an old nut. Many a mechanic on older cars would not be without his
faithful "smoke wrench." Machine shops also use a torch to heat and expand
parts that have a press fit. A gear that fits on a shaft may be heated with a special
"rosebud" tip that spreads the flame around a wider area, and when the gear has
expanded, it is picked up with tongs and slipped onto the unheated (and not expanded) shaft. When it cools off and contracts, the gear is securely fastened to
the shaft, but can be removed at a later time just by reheating it again.
Despite the versatility of the gas-welding equipment, it may not be the ideal
equipment for you, depending on your needs. If you have other uses for it besides
just welding, then it is definitely a must have, but, if you just need to occasionally
weld various thicknesses of steel together, some of today's electric welders may
be more suitable for you. Gas welding is harder to learn, there are more safety
problems in the shop when using a gas torch (especially when cutting), welding
thick metals takes good skills and it is easy to distort the parent metal when weld2-8

Types of welding
ing thin sheet metal. Automotive body men today are using a torch less and less
when doing repairs on thin metal. However, one of the advantages of gas-welding
equipment over any electric-welder is portability. Your gas welding cart can be
moved around anywhere without wires, even carried (when properly secured) in
your pick-up for welding at a remote site.
If you have the budget and the need for gas-welding's versatility and portability, then your ideal shop setup would include
both an oxy-acetylene rig and some kind of electric
welder.

Arc welding
Like gas welding, electric arc welding has
been around for almost 100 years, and the fact
that it is still around today illustrates its continued
usefulness. The official acronym for arc welding is
SMAW, which stands for Shielded Metal Arc Welding. The basic components of the setup include
the machine (the power source), a ground lead you
clamp to the work anywhere except where the
weld is to be made, an electrode lead which runs
from the machine to an electrode holder, which is a
handle with a clamp that holds consumable electrodes. The electrodes are metal rods covered with
2.13 In farm and construction equipment repair, most work is done
a coating.
with oxy-acetylene cutting and arc, or stick, welding. Arc welding is
In use, the weldor strikes an arc against the
not affected by wind outdoors, and is able to join or repair very
thick materials.
parent metal with the electrode, which completes
the circuit between the two leads and causes a
bright light and concentrated heat. Arc welding uses considerable
amperage of electricity to generate the intense arc, which melts the
parent metal. The central metal core of the electrode melts as the
work progresses, becoming the filler metal, while the fluxed coating
produces a shielding gas around the welding area that protects the
parent and filler metal from impurities in the air. Arc-welding produces slag as you proceed, a thick coating of impurities and deposits left from the rod's coating. This slag must be chipped off with
a chipping hammer, which is usually included with the machine.
There are a wide variety of welding rods (electrodes) available to
suit almost any purpose. The 12-14-inch-long rods are also called
"sticks", and you may often hear arc-wetding referred to as stick
welding. The rods vary in thickness, according to the thickness of
the metal you are welding, and also in alloy and flux-coating content. There are many special-purpose rods, and, because of the variety, rods are usually marked with a number at the beginning of the
flux coating, and different colors may also be added to the fluxes for
quick identification.
Rods are usually sold in boxes or cans of fairly large quantity,
which can be a problem for home/shop use where the welding is infrequent. The coatings on arc-welding rods are very susceptible to
moisture in the air, and must be stored in very dry, secure containers to remain effective. You may have seen welding filler rods in
gas-welding outfits stored in simple lengths of pipe welded to the
welding cart, but this is not suitable for arc rods. If you do purchase
2.14 Two endeavors you wouldn't think of together,
an arc machine, invest in several airtight metal containers to store
art and welding, combine today as many sculptors
the rods, even using bags of desiccant (moisture-absorbing crystals
and artists are now working in metals. Small works
usually found in small bags packed with cameras or sensitive elecare usually torch or TIG welded, with larger works
tronic equipment) in the cans.
like this one utilizing arc or MIG welding equipment.
2-9

Haynes Welding Manual
There are two basic types of arc-welders, relating to the polarity of the electricity they produce, AC or DC. The DC machines are generally larger, industrial
units found in production shops, where they are hard-wired in, or mounted in
conjunction with an engine for truck-mounted use in mobile field welding. Most
shop-type DC machines require shop-type electrical input, such as 440V or
three-phase 220V, which you will not find in any standard home. They are designed to operate day in and day out without overheating, and are considered
the best choice for welding really thick materials, so that is why we see DC arc
machines in use building bridges, buildings, ships, etc. There are a few small DC
machines for home use, but they have limited amperage and should be used on
lighter materials. There are even combination AC/DC machines, but these are
usually expensive shop machines.
By far, the most basic and practical home/shop arc-welder is an AC machine
often called a "buzz-box" because of the sound it makes when you are welding.
This is the least expensive single welding system you can buy, with a good
name-brand buzz-box costing about the same as a set of oxy-acetylene torches.
However, the arc machine comes with rods and everything you need, while the
gas setup also requires filled cylinders which make a ready-to-weld gas setup
about twice as expensive as a basic arc box.
The wiring you have in your house or shop will be a factor in choosing the type
of equipment best suited for your purposes. To use an arc machine, you'll need
220V availability. If you already have an electric stove in your house (or the house
had at least been wired for this) or an electric clothes dryer, you're probably in
good shape because many electric stoves and dryers use 220V current. However,
unless your dryer outlet is already out in your garage, you may have to have a qualified electrician run this 220V power out to where you'll be doing your welding. If
you don't already have a 220V outlet, the cost of running new service to your
garage may double the total expense of setting up to do arc-welding at home.
Also, welders do not just plug into the same outlet as your appliances. The
welder has a different arrangement of prongs on its plug, and an adapter is required to plug into a 220V appliance outlet. The outlet you use should also have a
good 20-30-amp circuit breaker as well. Note that there are some small buzzboxes that plug into ordinary household 110V power, but they aren't recommended for anything but light and occasional work.
A stick-welder is relatively easy to use. Unlike gas welding, where you have
to operate the torch with one hand while feeding the filler rod with the other hand,
there is only one piece to control with arc-welding, the rod-holder. However, the
rod starts out 12 to 14 inches long but is used up continually (gets shorter) as you
weld, making it tough to maintain an exact distance of rod to workpiece, which is
critical to a good arc weld. With the rod too close, you burn holes in the metal,
and too far away you can lose the arc entirely and have to restart. So the trick in
arc welding is control of the tip of the rod, and, because it is always getting
shorter, you have to "fine-tune" your wrist movement in the hand working the
electrode-holder. For this reason, most arc-welding is done with two hands, especially when learning. Use your other hand to steady and help control your wrist
action on the "working" hand. Professional weldors use arc-welding upside
down, laying on their back, hanging from scaffolding, or even underwater with
special equipment, but for the novice, a comfortable body and hand position is
very important to making good welds.
An AC arc-welder is well-suited to working on heavier steel materials, from
1/8-inch to 1/2-inch thick, but is difficult to control on thinner materials. The machine will have an amperage knob, with settings from 30-230 amps (depends on
make and model), which you suit to the rod and the work material and thickness.
Some of the more expensive shop machines have settings that go as low as 4
amps for light materials, but gas, MIG or TIG welding is- more popular today for
thin metals such as most automotive work. For fabricating shop equipment,
building a utility trailer, frame repairs or farm equipment maintenance, the buzzbox works fine.

2-10

Types of welding
To sum up the pros and cons of an AC arc-welder, the advantages include
the low initial cost, easy operation (with practice), versatility (it can be used indoors or out) and it offers a high level of dependability (no moving parts) and
quietness of operation. Disadvantages include: it's less practical for thinner metals, your shop may require rewiring to accommodate it, the home arc-welder
usually can't be used for welding long seams all at one time, you are restricted to
the limits of your power-cord length (as with any electric machine except the
generator-driven type), the welds may have considerable spatter and not look as
"clean" as other types if that is a consideration (such as in art projects, metal furniture design or street-rod fabricating), and there is the safety consideration of
potential skin burns. Compared to gas welding, arc-welding poses more danger
due to burns, not just from little spatters of hot metal, but from any skin that is
exposed to the UV and infra-red rays. You can get a severe sunburn from exposure (pro weldors wear heavy leather protective clothing) and observing an arcweld in progress without a helmet on, even for just a second or two, can cause
headaches and eye irritation.
The buzz-box was once the most practical home/shop welder, but increasing availability and affordability of home MIG machines in the last ten years has
put up a serious challenge to that title.

MIG (wire-feed) welders
This category of welding system has become one of the most popular for today's home/shop use. The initials stand for Metal Inert Gas, but is also listed in
technical descriptions as GMAW, for Gas
Metal Arc Welding. The basic elements of
the setup include a power supply (machine),
a torch with a large-diameter cable, a ground
wire with clamp, and a bottle of compressed
shielding gas. Inside the machine is a roll of
relatively-thin wire and a motorized transport
system for this wire.
In practice, you weld almost like arcwelding, but the electrode (wire) is constantly fed through the cable to the gun and
consumed at the weld. When you pull the
trigger of the MIG gun, you start the supply
of amperage (when the arc starts on your
work), the feeding of the wire electrode, and
the flow of shielding gas, which is also
routed inside the gun's cable
and comes out of the tip all
around the electrode, preserving the integrity of the weld like
the flux coating does on arc
rods.
The advantages of the MIG
system includes a much cleaner
weld than either gas or arc,
good versatility in materials with
the ability to do very well on thin
metals, and there is no electrode or filler rod to keep replacing. Control is easy because you
can set the amperage on the
machine and also infinitely adjust the speed of the wire com-

2.15 Anyone who is a fan of auto racing
is familiar with various types of welding.
In the immaculate shop of Larry Smith
Marketing, a crewman is putting a final
MIG weld on a complete NASCAR
chassis for a car like the Matco Tools
entry at left. Race car shops use a variety
of welding techniques, from gas to MIG
and TIG.
2.16 Small, portable wire-feed, or MIG,
welders have become one of the most
popular welding machines for
home/shop use. Easy to set up and
simple to operate, they produce very
clean welds, and models from 100-amp
to 140-amp can be operated on
household 110V current.

2-11

Haynes Welding Manual

2.17 Most MIG machines operate with a bottle of
shielding gas, but some are equipped to run with fluxcored wire which makes its own shielding gas as it
arcs, making the process more suitable for outdoor
and drafty situations. This home/shop-sized unit
shown is a combination machine that can operate
with gas shielding/solid wire, or the flux-core wire.
2.18 At the professional shop level, MIG welders are
all 220V machines, and offer power up to 250 amps,
which is enough to weld most anything. This
Millermatic 250 is a popular machine in fabricating
shops and automotive shops. There is even a model
of this machine with a small computer in which you
can store the welding parameters of up to nine
different jobs, in five different languages.

ing out of the gun. Various-diameter steel wires are available to weld material
from the thinnest sheet metal to 1/4-inch and 3/8-inch, as well as stainless-steel
and aluminum wires to weld those materials with. The weld from a MIG gun is
much cleaner than arc welding in terms of spatter, and there is no slag coating to
chip off.
Originally, wire-feed MIG machines were developed strictly for the professional shop doing long-duration production welding. A roll of wire in one of these
machines can last for an entire eight-hour shift without the weldor ever stopping
for a new electrode. Because the wire is machine fed into the weld puddle, the
heat and wire-feed rate can be tuned so that production welds can be made
much faster than with other systems. The MIG machine has been an expensive
piece of equipment in the past (and heavy-duty, big-shop models are still fairly
expensive), so it never used to be recommended to anyone for home/shop use.
However, less-expensive MIG machines have become widely available in the
past 5-10 years that have made these an excellent choice for the hobbyist, particularly the automotive hobbyist. These newer machines, mostly imported and
built with a few less features and a lower duty-cycle than would be required in a
production environment, have not only become very popular with the hobbyists
but are also are finding their way into more small fabricating shops, muffler shops
and race-car fabrication shops as a less expensive alternative to the big machines, yet with better speed and weld quality than arc or gas.
MIG machines range in size and features from "pocket" machines to large,
full-featured machines for shop environments that require 100% duty-cycle.
There are a number of smaller machines available today that operate on 110V
household current, which makes them very portable, and no garage rewiring is

2-12

Types of welding

2.19 If you're lucky, the welding store near you will
have a demonstration area, such as here at Altair
Gasses & Equipment, Oxnard, California. Here a
portable MIG unit is being tested where customers
can watch through a large safety lens (behind
operator, at right). You can get a feel for different
equipment before you decide what machine best
suits your needs.

2.20 If you are interested in cars as a hobby, whether it be kit cars,
street rods, race cars, or antique restorations, you should become
familiar with various welding techniques, and perhaps buy a system.
When fabricating parts at home, it's a lot easier if you have your own
welder, even if all you do is tack parts together and bring them to
someone else for final welding.

necessary. These smaller wire-feed machines usually have
4-7 heat range settings from 30 to 110 or 140 amps, and
can handle light sheet metal such as auto body material up
to metals as thick as 1/4-inch or 3/8-inch (less maximum
thickness is possible on aluminum). They either have
wheels on the bottom or have optional, wheeled carts that
make then very easy to move around your shop or garage.
Many beginning weldors like to build their own welding cart
as their first project with a new welding machine.
The shielding gas used with MIG machines can be CO2,
Argon, or a mixture of the two, depending on the materials
you are welding. The basic gas used most often is straight
CO2, because it is the least expensive. Various sized gas
bottles are available from small, very portable 20-cubic-foot
bottles (about two feet high), to 120-cubic-foot bottles (four
foot high, six-inches in diameter) that can supply enough
gas for eight hours of continuous welding. The small bottles are fine for occasional home/shop use where long seams are not welded regularly.
One of the factors that has made MIG welders so popular with home/shop
users is the relatively easy learning curve associated with using them. Given a little instruction and practice, most people can be up and welding a decent bead in
an hour or two. We're not suggesting that that person would then be ready for a
full-time job as a weldor, or that his/her first welds would pass rigid specifications
for nuclear reactors, but the wire-feed machines are easier to learn than most
other systems. One of the factors that makes it easier is of course not having to
deal with feeding the filler rod in with your other hand. In automotive body work
this can be particularly helpful when you have to hold something with your left
hand, like the alignment of two pieces of sheet metal, while you tack them together with the one-hand MIG torch. Torch position is very important in all forms
of welding, and the fact that the distance of the MIG tip from the work is constant
(in many cases the nozzle is actually touching the work to steady it) makes controlling the weld much easier.
After selecting the proper heat setting based on the thickness of the material

2.21 Typical home/shop projects
such as a utility trailer, race-car
trailer, metals rack, shop cart, engine
stand, hoist and much more can be
built at home with either MIG (shown)
or an AC arc welder.

2-13

Haynes Welding Manual

2.22 Street rodding and antique car
restoration frequently require welding
on old, even rusty sheet metal body
panels. Here the lower portion of a '32
Ford cowl has been patched with new
steel to replace rust-out area. The
panel was MIG-welded in with a 110V
welder, ground down with a bodysander, is ready for finishing and
another 60 years on the road.

you are welding, the only other variable to control is the
speed the wire is fed into the weld puddle. If the speed is
wrong, there will be a lot of sputtering and uneven welding
and penetration. Most MIG weldors tune the wire-speed in
by sound, They set up on a scrap piece of metal with a wire
speed that may be too slow or too fast, then pull a bead
while adjusting the speed. When the right speed is reached,
the MIG welder gives a distinctive crackling sound to the
procedure. The steady crackling sound means you have the
right wire speed.
There are three basic types of small MIG machines.
Those that use plain wire with a bottle of shielding gas,
those that use flux-coated wire and no gas bottle, and combination machines that can run either fluxed or plain wire.
The flux on the wire functions the same as the coatings on
arc rods, creating a shielding gas as the wire is consumed.
The bottled-gas-shielded MIG welding is the preferred
method for indoor welding where clean-looking weld beads are desired. However, the shielding gas around the weld process is subject to being disturbed by
air currents, so for outdoor welding (such as farm equipment repair, fence construction, etc.) the fluxed-wire machine is better. The weld isn't quite as clean as
with the gas, and fluxed wire doesn't do as good a job on thin sheet metal (under
18-gauge) but these machines are more practical for the outdoor work, which is
usually on heavier materials anyway. Also, the fluxed-wire machine never need to
have a bottle refilled, so as long as you have plenty of wire inside the machine,
you can't have your work delayed by running out of shielding gas.
Considering all of these factors, the modern MIG machine may be the most
practical type of machine for many do-it-yourselfers, particularly the automotive
hobbyist, who has to make very clean welds, both with thin sheet metal as well
as heavier chassis work. The ease of operation, maneuverability around the shop
(with the 110V machines), one-hand torch operation and the gentle learning
curve have combined to make many first-time MIG weldors tackle their projects
with confidence.

TIG (heli-arc) welding
This is unquestionably the "Rolls-Royce" of the welding processes in many
ways. The lettering stands for Tungsten Inert Gas, but many weldors refer to it as

2.23 Basic components of a TIGwelding system. Very similar to
operating a gas torch and using your
other hand to feed filler rod, TIG
produces the cleanest welds with the
least amount of material warpage,
and is the best system for thin, highstrength material like chrome-moly as
well as aluminum.

2-14

Types of welding

2.24 While TIG or heli-arc welding is considered by many to
be the most controllable welding technique, it takes more
practice than any other. You have to learn to manipulate the
torch with one hand, the rod with the other, and the amperage
control with your foot on a pedal. There are no sparks, spatter
or slag. Here an aluminum frypan's handle mount is being
repaired. The heli-arc welding didn't even bother the nonstick coating on the other side!

heli-arc welding, though this is a trade name established by
the Linde Corporation many years ago. The name refers to
the fact that back then, helium was used as the shielding
gas for the process, though today argon is the most commonly used gas for TIG welding. Either shielding gas has
the capacity to exclude foreign materials during the welding
process, as well as being unable to combine with other elements to form chemical compounds detrimental to the weld
2.25 Where TIG welding really shines is in two tough
integrity. The process can also been seen abbreviated as
situations in one job, like thin materials and aluminum, such
GTAW, for Gas Tungsten Arc Welding.
as this part that looks like something from a space ship. This
The basic components of the TIG process include a
wound up being a belt-pack of controls for a big piece of
welding machine, a torch with a tungsten electrode, a
machinery - the operator strapped this to his waist. Aluminum
ground cable, a foot-operated amperage control pedal and
is tougher to weld than steel because it doesn't change color
a bottle of compressed shielding gas such as argon. It difas you heat it. When it melts it turns shiny, but tarry a little
longer with the torch and the material has holes in it. Don't
fers basically from stick welding and MIG welding in that
tackle a project like this until you have mastered the process.
the electrode is not consumed, and filler rod is separately
hand-fed into the weld puddle when needed. In operation,
the machine is turned on, the weldor brings the torch close
to the work and depresses the foot pedal to start the arc. Current flows through
the tungsten to the workpiece, creating an intense but concentrated heat that
melts the parent metal, with the operator controlling the amperage with the footpedal while welding, and feeding the appropriate filler rod to the puddle as
needed. The tungsten electrode has a very high melting point and is not consumed.
What makes the heli-arc different in practice from other systems is the higher
operator skill required, since the weldor has to coordinate with both hands and
the foot pedal, all of which affects the quality of the finished weld. Unless you are
already an accomplished weldor with an oxy-acetylene gas-welding torch, you'll
find the TIG process takes a lot of practice.
TIG welding produces the cleanest, flux-free and spatter-free beads with virtually no contamination. For this reason, it is the method of choice for such critical applications as race cars, aircraft, missile construction and nuclear reactor

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Haynes Welding Manual
welding. The TIG welds are strong, ductile and corrosion-resistant with virtually
no cleanup required, making it popular for welding of surgical, medical and foodservice equipment, especially on stainless-steel. There is little smoke produced
during TIG welding and no flying sparks, and without the smoke and sparks the
weldor can more critically observe the welding action as he goes.
While there is a lot of skill required in TIG welding, its ability to handle all
kinds of metals of varying thicknesses, the ability to reach into corners and hardto-access areas to weld and its outstanding ability to mate thin metals without
putting excessive heat and distortion into a wide area on either side of the weld
has made the heli-arc method particularly useful in race-car and other critical
construction applications. The types of metals that can be welded with TIG machines include: all steel alloys, aluminum alloys, aluminum castings, stainlesssteel, copper and nickel alloys, magnesium and exotic metals such as titanium
and zirconium. It is one of the few systems that can tackle welding dissimilar
metals and joining metals of different thicknesses. It's been said that a skilled TIG
weldor could join a razor blade to a railroad track, though there isn't much call for
that.
The torch for TIG welding is smaller and lighter than most other welding
torches, allowing for greater weldor comfort when welding for long periods. For
production welding, most TIG machines are equipped with a water-circulating
system to keep the torch cool. In use, a water pump circulates filtered water from
a storage tank out through the main cable to the torch head and then returns the
heated water back to the tank. Many cooling units employ a small radiator and
electric fan to cool the water. Where lots of production welding is done, a large
water storage tank is used, or the water is fed in cold from the shop's plumbing
and the heated water is plumbed back into the drain system, so heated water is
never circulated back through the torch. The TIG machine requires shop-type
current input (230V/460V/575V single-phase or 230V/460V three-phase) and
connections to and from the water-cooling equipment, making it one of the least
portable of welding systems.
Because of the electrical requirements and other hookups, the steep operator learning curve, and the considerable expense of the most shop-type TIG machines, this has never been a system that has penetrated much into the
home/shop and hobbyist market. Rare and proud is the automotive hobbyist or
racer who has a heli-arc machine at home, and who knows how to use it to its
capacity. The process has assumed an almost "mystical" aura to automotive
fans because of its use in race-car construction, and even otherwise skilled
home weldors will bring certain components like critical steering gear to a professional to have the parts TIG-welded. Street rod builders love it for the quality of
weld, which is often cosmetically appealing enough to require no grinding or filling to make the welded part ready for painting or even chrome-plating.
Shops with TIG machines rarely take advantage of this, but most TIG welding machines are capable of also performing stick welding if the job should require it. TIG welding is ideal for thinner materials, but if a job required joining
some one-inch-thick plates, the stick-welding mode would be much faster. The
arc capability would also come in handy if the job required some welding outdoors or near a drafty doorway, where the draft could blow the argon shielding
gas away and cause an erratic weld. Switching to the arc mode simply requires a
switch on the machine be thrown to the correct current position for arc, and the
arc "torch" electrode cable plugged in. When in the arc mode, the foot control is
deactivated and the weldor sets the amperage on the machine with a knob, like a
straight arc machine.
While most production shop TIG machines are large, expensive, heavy-duty
machines with water-cooling systems for the torch, there have been strides in the
past ten years at making a more affordable TIG machine. Today there are several
to choose from which are air-cooled instead of water-cooled, reducing cost and
complexity, that feature straight 220V, single-phase input connections for simplified electrical hookup, and have lighter-duty, less-expensive internal electrical

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Types of welding
components. These new machine are one-half to one-third the cost of their bigger conventional TIG brothers.
Because of these factors, there are more small shops that today can afford
the benefits of TIG welding, such as high-quality welds on thin materials, and the
ability to weld beautifully on non-ferrous materials like aluminum, even cast aluminum. The are often seen in large engine rebuilding facilities and automotive
machine shops, where they serve their time repairing cracks in aluminum blocks
and heads, expensive parts that would otherwise have to be replaced if such repairs could not be made. However, these "economy" TIG machines can't do
everything the big ones can, particularly when it comes to torch cooling. If long
welds are to be made, the air-cooled torch will get too uncomfortable to hold.
Also, the smaller, less-expensive electrical components inside will not have as
long a duty-cycle as the big machines (more on duty-cycles later), but in a small
shop fabricating race-car or street rod parts and doing precision chassis work,
long, continuous welds are not often encountered.
Some welding machines today offer "convertible" adaptability. Kits can be
added to some MIG machines to add heli-arc capability, and there are kits with a
different torch and a separate wire-feeder to use the output of the bigger TIG machines as a MIG machine, but this convertibility usually puts the machine out of
the home/shop price range.
Even with the introduction of this new generation of more-affordable TIG machines, this is still a system that isn't practical for the average home/shop weldor
to get into. As with oxy-acetylene gas welding, the practice time it takes to be
good with a heli-arc torch requires consistent, daily operation, and most occasional weldors just can't get enough time on the machine to really do well. Most
basic home/shop fabrication and repair projects do not require the "reactor-quality" welds and superior cosmetic appearance of TIG welding, and even the economy TIG machines cost more than twice what other starting welder setups cost,
making the gas welder and small MIG machines still the most versatile equipment for home use. A drawback of TIG welding is that it is a slow process, so for
a project like building a utility trailer, a typical home MIG machine would be much
faster.

Duty-cycles
In any discussion of electric welding processes, the term duty-cycle comes
up and is a source of some confusion to the beginning weldor. Basically, the bigger, heavier and more expensive pro-shop type welding machines have transformers and other internal electrical components designed to operate for long
periods of time without overheating. Smaller, home-type machines can't operate
as long, because the internal components had to be made less expensive in order to reduce the overall costs to a "consumer" level.
The official quantifier of such work capability is called the duty-cycle. It is expressed as a percentage, such as a "40% duty-cycle." What this refers to is a
ten-minute period in a laboratory welding test. At a 40% duty-cycle, a particular
welding machine is capable of welding for four minutes out of ten. In other
words, if you welded non-stop for four minutes straight, you would have to let the
machine "idle" for six minutes before resuming welding, allowing the internal
components to cool off. The maximum current that a welding machine can draw
from its components is limited by the temperature rise of those parts, and the
temperature goes up with the square of the current draw.
Bigger, more professional and more expensive welding machines will have
higher duty-cycles because of the nature of the work they have to do. There are
some cases where a robotic or machine-driven automatic welder must be capable of 100% duty-cycle because it is operated continuously, but this is unusual.
The advertised duty-cycle of a welding machine is usually given at the maximum current draw of the machine, the highest amp setting. This setting of course

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Haynes Welding Manual
is required only when welding the thickest material the machine is capable of. As
the amperage setting of a welding machine is reduced, the effective duty-cycle is
increased, so that there is somewhere on the welding machine's "curve" a point
where the duty-cycle is close to 100% at some amperage setting.
For the home/shop user who is rarely welding anything thicker than 1/4-inch
or 3/8-inch mild steel, the duty-cycle is not a problem. However, it's important to
know what the duty-cycle for your machine is at various amperages, and especially to understand the term when shopping for a machine. For instance, one
popular introductory-level 110V MIG machine has an amperage range of 30-110
amps. Right away, you know that such a machine is not really designed for long
welds on heavy materials, because the maximum amperage is only 110. Further,
the advertised duty-cycle for this machine is 95% at the 30-amp setting, but
25% at the highest amp setting, showing the difference in how the current-draw
heats up the components. Depending on your average welding needs, such a
machine may be just fine, handling short welds occasionally on 1/4-inch steel,
and longer periods on thinner material. Most automotive sheet metal, for instance, seldom requires an amperage setting above 30, and even the small MIG
machines have a long duty-cycle at this setting.
Generally, welding machine price goes up with maximum amperage and
duty-cycle. You can roughly compare the performance of the machines being
considered by comparing their duty-cycle at the amperages you will most often
be using. A feature to look for on some of the better machines is an "overheat"
protection circuit and warning light, which may save you the cost of a burned-out
component. Some machines automatically shut down when the overheat circuit
kicks, and in others an internal electric fan comes on to speed the cooling process, but like most "bells and whistles" these features usually cost a little more.

Plasma arc welding
and cutting
This is another welding/cutting process that has developed in the recent
past that was once considered exotic, yet is now filtering down to lower price
levels in the welding marketplace. The nomenclature refers to the plasma state of
a gaseous material, in which the material is heated so much that the gas conducts electricity. What makes PAW (Plasma Arc Welding) so different is that the
flow of superheated gas actually makes the welding arc, with the metal electrode

2.26 Plasma cutting is rapidly
replacing oxy-acetylene cutting in
many home and shop applications.
Used either as a mechanized cutter or
by hand, the system is simple to
operate, and makes a faster, cleaner
cut with much less sparking and less
heat induced into the parent metal.

2-18

Types of welding
safely hidden way up inside the torch body away from the welding
action.
The plasma welder makes a hotter and easier-to-control arc
than even the much-touted TIG welder. The arc becomes a narrow column of heated gas (usually argon or nitrogen) that can be
directed as precisely as a surgical laser. A second gas is plumbed
through the torch to maintain a gas shield over the weld area, as is
done in most electric welding. The extremely-high temperature of
the plasma arc means that higher welding speeds can be used in
production applications, and where there is a close fit of the two
edges being welded, as is usually the case in a production situation with newly cut materials, often the plasma weld is accomplished with no addition of filler material when welding thinner
stocks. This has made it a preferred system for some industrial
applications.
In operation, the plasma equipment looks much like TIG
equipment, except that there are two bottles of gas, and the torch
is designed differently inside. The very dense, very hot "flame"
does not require as precise an arc-starting-distance of the torch
to the material, making plasma equipment somewhat easier to operate than TIG, especially on projects where no filler metal is
needed. In TIG-welding, the weldor must strike an arc with his
tungsten electrode With the plasma method, however, the electrode is too far up inside the torch head to get near the parent
metal, so most of the plasma machines have high-frequency arcstarting circuitry that makes them easy to get up and running, using the hot gas column to start the arc, after which the proper
torch-to-work distance is easily established by the weldor.
While there are specialized applications where plasma-arc
welding is the preferred method, its widest area of usage today is
in cutting. The column of plasma-stage-heated gas is hot enough
2.27 In fabricating shops, a large 220V (or higher
to cut through virtually any material at almost any thickness. On
current, three-phase) plasma cutter is used, capable of
cutting thick materials and traveling at fast cutting
thin materials, the plasma cutter goes through as fast as the operspeeds. Most plasma cutters are used without
ator can move the torch (speeds up to 100 inches per minute),
shielding
gas, using air from the shop air compressor
and even on 1/2-inch-thick steel the moderate-size cutters can
to cool the torch and form the ionized gas column
cut at 15 inches per minute, which is about one inch every four
under the tip that creates the arc.
seconds!
While the speed of the plasma cutter is exceptional, it is the
quality of the cut that has made it so popular today in many applications like automotive, duct repair and fabrication, and medical or food-service equipment
work. The plasma cutter will cut virtually any ferrous or non-ferrous material with
equal ease, even on aluminum and stainless where ordinary torch cutting is difficult without considerable pre-cut and post-cut cleaning.
Since there need be no direct contact between the torch and the work material, plasma cutting doesn't involve a lot of spatter getting into the torch head,
and most materials can be cut with no pre-cut cleaning. This is especially important to automotive users, who can make clean, fast cuts in sheet metal, whether
it's painted, rusty or dirty. The concentration of the narrow cut and the speed the
plasma torch can travel means that the cut edges are many times cleaner than
even a machine-cut edge from an oxy-acetylene torch. There may be little or no
cleanup of the cut edges required, depending on the job requirements, and the
cut edges are not only smooth but uncontaminated, so that plasma-cut edges
can generally be welded together much easier that edges cut with a gas torch
where oxidation must be ground off before welding.
Plasma cutters have become particularly popular in machine-cutting operations where the torch head is mounted on a machine that has a pantograph
arrangement. The weldor moves an arm around a wood, paper or metal template
and the cutting torch cuts that exact shape out of metal. Sometimes, several cut-

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Haynes Welding Manual

2.29 Eventually, you will find yourself at a steel supply store, shopping for
plate, angle-iron or tubing for a project. Steel is usually sold in 20-foot lengths,
but it's often cheaper to buy steel here than at a home/lumber type store.

2.28 Where the really complete
home/shop setup was once an AC arc
welder and a set of gas torches, today
more shops utilize a MIG welder and
plasma cutter. This welding cart
features a gas-shielded 130-amp MIG
and a plasma cutter capable of
cutting up to 3/16-inch material, and
both machines operate on household
110V current.

2-20

ting heads are operating on a large sheet of metal plate, cutting three or four
copies of the template out at the same time. The clean plasma cuts mean less labor is required to make a finished part.
Metal cutting has been done for decades with oxy-acetylene equipment, but,
besides the clean-cut edges, a plasma cutter has one other major advantage
over the oxy-acetylene torch. Since the main component of the air around us is
nitrogen, which make a good inert gas to superheat into a plasma flame, common air can be used as the cutting gas. This is usually supplied simply by hooking the welding machine up to a standard shop air compressor making 75 psi.
Not only is the compressed air virtually free, with no bottles to fill, but plasma
cutting involves no flammable gasses in dangerous high-pressure cylinders.
There is a major savings in bottled-gas costs, convenience, and shop safety.
The nature of the plasma-cutting process is such that very little spark spray
comes from the cutting action, and there is virtually no discoloration or distortion
of the cut edges. It is almost like "cold" cutting. These attributes make the
plasma system the method of choice now in automobile wrecking yards for cutting up cars for dismantling. It's much faster than a gas torch, and the chance of
fires starting from flying sparks and droplets of molten metal is greatly reduced.
Plasma cutters have been operated in such situations with torch hoses as long
as 234 feet, with the welding machine kept indoors in a shed and the operator
wandering around the yard with the torch, not having to transport a heavy cart
with bottles of compressed gasses. Body shops love it for its clean edges and
the ability to cut an exterior body panel with less chance of igniting undercoating,
paint or burning a hole in an interior panel with a stray blob of molten metal.
Although the technology sounds complicated, plasma equipment is perhaps
easier to maintain than gas, MIG or TIG equipment, and the learning curve is not
as steep. As with the modern MIG and TIG machines, recent years have seen the
price of plasma-cutting equipment come down considerably, and this has put
the technology in the hands of many automotive shops. Most home/shop users
will not have enough cutting work to do to justify owning a plasma cutter, but
when a lot of cutting needs to be done, and done more safely than with traditional gas, this is definitely the way to go. If you are around a body shop or fabri-

Types of welding

2.30 If you can't carry a 20-foot length of steel home with you,
steel houses will generally make one "courtesy" cut for a
small fee. Any cuts after that are expensive, so it's best if
you have some method at home for cutting the metal for
your projects.

2.31 This steel supply store has a neatly-organized rack
for materials, in which each different thickness of material
is identified by a different color of paint on the ends,
which makes shopping a lot easier for hobbyists without
a micrometer.

cation shop that has a plasma cutter, see if they will demonstrate it to you. You'll
find it amazing when you see how fast it cuts, how little spark spray there is, and
how clean and relatively cool the cut edges are.

Practice and training
When it comes to hand-eye coordination, everyone has a little different skill
level to start with. How easily each person can pick-up a welding machine, read
the instructions and begin joining metals together will differ with that person's
mechanical background. Some people seem to flow into the work intuitively; others require considerable practice and often a little coaching from someone who
can weld already.
Each of the welding systems we have discussed in this chapter requires a
different amount of practice and skill to master, but rest assured that even if you
have never done anything like this before you can learn to weld. Millions of men
and women have learned to do this in the past. During the domestic manpower
shortages of W.W.II, there were many housewives who went to work in the defense plants, and even though they had never done anything mechanical they
were there riveting, metal-shaping and welding on aircraft, tanks, ships and many
other critical projects.
The first step in deciding what kind of equipment you need is to accurately
assess the kinds of projects you would do most often if you had welding equipment in your home/shop. The thicknesses of metals you want to work with, the
types and alloys of metals, the kind of electrical power you have available and
the length of the welds you may need to perform are all factors in choosing the
right machine. We've given you enough of a brief outline of the advantages and
disadvantages of each type of equipment to aim you in the right direction. You
may also want to consult with your local welding shop and local welding supply
store before making your decision. If you know someone who already has a
welder at home, ask his advice and even see if he will let you try out his equipment on some scrap pieces.
Most people who are serious about picking up welding skills and doing it
right can benefit from actual training. Your local community college may have
adult evening courses in basic welding, or there may be a trade/technical school

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Haynes Welding Manual
nearby. Courses offered at publicly-funded community colleges and trade
schools are usually inexpensive, and the hours are often built around a working
person's schedule. There is a real difference between a weld that looks good,
and a weld that performs well. If you practice welding on your own, you may
achieve welds that look OK to you, but which may fail in actual use. One of the
valuable parts of the training you will receive in a legitimate course is the critique
from the instructor. He can show you how to test various trial welds for strength
and let you know when you're getting it right. We think such training is invaluable
if you plan to do anything more involved than repairing a bicycle or garden tool.
Good training shortens the learning curve dramatically, and we recommend it to
any readers who have it available in their area.

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Oxy-acetylene gas
welding/cutting
Perhaps because of its history going back to the turn of
the century, or perhaps due to its appearances in films and
other popular imagery, gas welding/cutting has the most
"romantic" image of the various welding systems we'll deal
with in this book. When most people conjure up a vision of
a weldor, it is of a perspiring, leather-clad man wearing dark
goggles and wielding a flaming torch with sparks flying
everywhere. In truth, this is more likely a picture of someone cutting with a torch rather than welding, but it points
out the ubiquitous nature of the gas equipment in the overall welding picture.
Although losing some ground to modern electric
welders in the most recent decade as the welding system
of choice for the average home/shop user, oxy-acetylene
equipment is still unarguably the most versatile setup for
home, farm or shop. Besides its function as a fusion-joiner
of metals, gas equipment also of course is extremely valuable as metal cutting equipment, and can also be used for
non-fusion metalwork such as brazing, soldering, and the
dying art of automotive body lead work. It is also useful
equipment in any automotive shop for freeing rusted fasteners, heating machined parts that require a hot shrink-tofit connection (like a gear on a shaft) and heating metal
parts prior to bending them. It requires no water or electrical connections, making it one of the most portable of systems, you can load it into a pick-up truck and take it to any
remote location. If the gas hoses are long enough, the weldor can climb up a pole or down a shaft to perform welding
or cutting, a flexibility few other welding systems can
match.

3.1 Versatile gas-welding equipment has been a mainstay of
metal fabricating for most of the 20th century, and little has
changed with procedures or equipment. The basics, fusing
metals at their melting point, are still valid for many uses in
farm, industry and home/shop hobby applications.

The basic gas
process
When gasses are used in other types of welding, they
are usually of the inert kind, like argon, CO2 or helium,
which are involved in the welding process only to keep the
molten weld puddle clear of impurities from the air during
formation. In oxy-acetylene welding/cutting, however, the

3.2 You'll find helpful people at your local welding supply
store that can set you up with torch equipment, oxygen
and acetylene bottles, and other supplies you'll need.

3-1

Haynes Welding Manual

3.3 Look in the corner of almost any automotive or
fabricating shop and you'll a setup just like this, with bottles,
regulators, hoses and torch neatly corralled in a portable
welding cart. Carts can be readily purchased, but most
beginners like to make their own cart as their first project.

3.4 This is typical of a good, general-purpose welding, cutting
and heating set, ideal for automotive, muffler shops, farm
and trade schools. Starter sets have smaller torches and
10-12 foot of hose, bigger sets have larger torches and
25-foot hoses.

gases are what make the flame itself. Acetylene gas is quite flammable, and
combined with oxygen, which by itself does not burn but speeds up the oxidation
or burning of any other fuel, makes one of the hottest possible gas flames (56006300° F),suitable for the rapid welding, cutting or heating of most ferrous and
non-ferrous materials. Although all compressed gasses pose some shop hazards
because of the pressure inside the bottles, oxygen and acetylene are considerably more dangerous to work around, and require much more caution and close
attention to safety rules.
Oxygen, while not exactly flammable by itself, is the gas necessary both foi
us to breathe and for any type of combustion to take place. Combustion is really
nothing more than very rapid oxidation, and if pure oxygen is directed at some
thing flammable, a fire can start very easily. Some inexperienced weldors hav<
been know to dust off their work clothes with their unlit gas torch, but the extn
oxygen that gets into their clothes can make it so flammable that any tiny sparl
could start the clothes on fire. Likewise, oxygen gas must be kept away fron
things like oily rags or any petroleum products. Oxygen as used in welding equip
ment is generally stored in high-pressure, 1/4-inch-thick-walled steel cylinders s
2200 psi. While oxygen may be important for our lungs to work, it can still be dan
gerous if too much is introduced to the bloodstream. For this reason, oxygen ga
should be kept away from open cuts such as you might have on your hands.
Acetylene gas, on the other hand is flammable to the point of being explosivt
and is also mildly poisonous, causing nausea and headaches if you breathe muc
of it. Older readers may remember using a "carbide cannon" on the 4th of Jul
when they were kids. A small quantity of pellets were put into a small met;
3-2

Gas welding/cutting
cannon which held some water. A gas was produced inside that was lit by a flintsparker mechanism on top, and the result was a tremendous bang. The pellets
were calcium-carbide, and the gas produced was acetylene.
Pressure in the acetylene gas cylinder is much less than with oxygen, at 250325 psi, but the construction of the cylinder is different. Acetylene cylinders are
shorter and fatter than oxygen bottles, and are constructed in two halves. Because acetylene is unstable at high pressures, the only way to get sufficient quantities into the standard bottle is to dissolve the acetylene in another medium. In
welding tanks, the two halves are filled with an asbestos/cement mixture and then
welded together. After baking, the material forms a honeycomb inside the tank.
Liquid acetone is put into the tank because it will absorb 25 times its own volume
in acetylene gas, thus stabilizing the acetylene.
Because of the differences in chemical action and storage of oxygen and
acetylene, there must be no mix-ups between the two. For this reason, the tanks
are made in different proportions and different colors; the acetylene bottle has
only left-hand threads, and the hoses for each bottle are different, i.e. red hose for acetylene, green hose for oxygen
(see illustration). Both bottles have a threaded top for filling
and connection of the regulators, and due to their high internal pressure, especially the oxygen cylinder, gas bottles
should always be stored securely. If a bottle were to fall from
a truck onto concrete, for instance, the regulator could be
knocked off, suddenly releasing enough gas to propel the
heavy bottle around like a kid's balloon, except with potentially deadly force. In addition, the acetylene bottle should
always be stored in an upright position. If stored laying
3.5 There must be no mix-up of gasses, so oxygen hoses
down, some of the liquid acetone inside could be drawn out
are colored green, acetylene hoses red, and the acetylene
of the bottle into the welding supply, ruining the weld.
hoses have left-hand threads, identified by a groove
cut around the fittings.

The equipment
Besides the two gas bottles, there are gauges/regulators, hoses and the torch itself (see illustration). Each gas
tank has it's own set of two gauges mounted on a regulator
body designed to reduce the high cylinder pressure down
to a useable pressure for the torch. On each tank, there is

3.6 The gas bottles are fitted with valves, to which regulators
are attached. This is a cutaway of an oxygen cylinder valve,
showing the way the valve seals internally. Oxygen cylinder
valves seal best when either closed or fully open.

3.7 Heavier-duty torch sets like this Trade Master from
L-TEC have torches capable of welding up to 3/8 steel,
cutting up to 1 1/2-inch steel, and heating capability
of 103,000 BTUs per hour.
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Haynes Welding Manual

3.9 Cutaway of a single-stage regulator shows how the
cylinder pressure is adjusted down to a usable range for
welding. There are two gauges attached, one shows
the total pressure left in the cylinder, and one shows
the adjusted pressure supplying the torch.

3.8 Highly portable "Kangaroo" outfit has everything you
need in a small package, including a polypropylene carry
cart. This doesn't have a lot of welding-time capacity, but is
popular for maintenance work, metal sculptors, and
automotive shops that don't use a torch too often.

3.10 The gauge/regulator setup screws onto the tank's
cylinder valve, and has a fitting for attaching the
hose leading to the torch.

3-4

one gauge to indicate the pressure in the tank, while the
other gauge reads the pressure after the regulator, which is
the pressure delivered to the torch and a very important adjustment in oxy-acetylene welding.
There are two basic types of regulators found on gas
welding setups, single-stage and two-stage. The former
type reduces the cylinder pressure to a working pressure in
just one step, say from oxygen's 2200 psi to 3 psi for the
torch (see illustration). In the two-stage regulator, the first
stage reduces pressure to about 30 psi; the second stage
adjusts pressure from there down.
A great portion of the expense in a gas-welding setup
comes from the gauges/regulators, and better ones simply
cost more. The simpler-to-manufacture single-stage regulators cost less and are therefore commonly found on the lessexpensive kits for oxy-acetylene welding (see illustration).
They work fine for most purposes, and their only drawback is

3.11 Connectors are available to add more hose onto a
starter set for a longer working distance if you need it.
These screw into your hoses and the extra new
hoses screw on the other side.

Gas welding/cutting
that the regulation depends heavily (excuse the pun) on the pressure inside the tank. As the tank pressure goes down as the gas is used up,
the regulation changes and must be adjusted again. Also, when doing a
job that requires a lot of gas flow, such as large welds or cutting/heating
thick plates, the single-stage regulator may not be able to keep up. The
more expensive two-stage regulators maintain gas flow to the torch
with less fluctuation, which is important in a professional welding operation but may not be a big factor in home/shop welding if you don't
work on heavier materials. Obviously, gas-welding sets with two-stage
regulators will cost more initially than the single-stage kits.
The hoses for a gas-welding setup are specially-designed to carry
the oxygen and acetylene gasses. While they do not handle the very
high tank pressures, they are built in three layers to withstand the regulated pressures for many years with proper care and maintenance. As
mentioned above, the hose for carrying acetylene is red, while the oxygen hose is green, and the acetylene hose has left-hand threads on its
fitting, so there is no chance of mixing them up when making connections (Note: Left-handed fittings generally have a groove cut in around
the fitting, to differentiate them from normal, right-hand fittings). Doing
so could be disastrous, since any residual flammable gas or other material in a hose connected to pure oxygen could cause the hose to ignite or explode. For this same reason, it is important that no lubricants
or chemical compounds of any kind be used on the hoses or fittings.
Gas-welding packages may contain hoses around 10-12 feet long in
the economy or light-duty kits, and 20-25 feet long in the heavier, more
professional sets. Extension hoses can be added to your starter set if
you need to reach areas further from your tanks (see illustration).

3.13 In this clever setup, the hoses and torch are
attached to a swingaway arm for access to the tanks
for servicing. Arrow indicates retaining plate with a
simple steel wedge rod. Tanks are held securely but
can be changed quickly without wrenches.

3.12 In industrial situations, like this oilfield service
truck, gas welding setups may be equipped with
large cylinders and 100 feet of hose, to handle
any situation.

3.14 Basic torch sets include, from top: cutting torch attachment,
basic torch head, a variety of welding tips sized for different
thicknesses of material, and at bottom a rosebud tip for
heating large areas.

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Haynes Welding Manual
The torch for oxy-acetylene welding is a precision-made
tool, usually constructed with a forged brass body, two knobs
controlling the gas flow, and copper tips of varying size (see illustration). In use, the two gasses flow through valves controlled by the knobs, and mix inside the torch with the combined gasses coming out of the tip in an oxygen-to-acetylene
ratio controlled by the weldor. The weldor changes tips, each
of which has a carefully sized opening, to suit the gas-flow and
flame shape required for a particular job. The makeup of the
cutting torch is different from the welding torch and will be discussed later on.
Gas welding sets can be purchased three ways: as a welding-only setup, a cutting-only setup or a combination set with
two torches. The type you choose will depend on your needs. If
all you need to do is weld up animal corral fencing made from
steel pipes, you may use a cutting-only gas set for cutting pipe
to length and shaping the cut ends to fit against the next pipe,
3.15 When assembled with welding tip and hoses, this is
and use a generator-driven arc welder on your truck for joining
what an oxy-acetylene welding torch looks like. The two
the pipes. However, if you are doing automotive sheet metal
gasses are controlled by separate knobs, and are
mixed inside the torch body.
work or metal sculptures with relatively-thin materials, you will
probably do most of your cutting with an electric shear, hand
tin snips, hacksaw, etc., and only require a torch for welding, brazing and occasional heating. A combination set is of course the most versatile. Most sets that
you buy can be fitted with a different torch at any time, so if you decide to buy a
welding-only setup, you can purchase a cutting torch later on if your need to.
After you purchase your welding package, you will have to buy or rent tanks.
The standard-size oxygen and acetylene tanks will hold enough gas to last the
home/shop user for a long, long time. The tanks must be hydrostatically-tested
periodically, which involves filling them with water to a certain pressure to test for
safety. When the test is due, your local gas supply cannot refill your tank until it is
tested. When you buy new tanks outright, you then become responsible for the
testing costs and any cylinder-valve repairs, while if you lease the cylinders, the
gas company takes care of that as part of the lease agreement. Leasing the cylinders allows you to get started welding with the minimum investment, because
outright purchase may be expensive. However, if you add up the monthly rent

3.16 You'll never have cause to disassemble your torch this far, but these are the internal components. Some torches require
wrenches to change tips and heads, while others have knurled, hand-tightened connectors.
3-6

Gas welding/cutting

3.17 Each of these little "flea circus" figures are welded up
completely of thin welding rod and tiny blobs of molten metal.
The artist works with a very small welding tip and tremendous
patience, showing what can be done with skill
and imagination.

3.18 The small, medium and large welding cylinders contain
80,150 and 275 cubic feet of gas, but some manufacturers
label theirs by a letter designation. Ask your welding supply
shop approximately how long each size would last in terms
of welding, and choose according to your needs.

charges, you'll find that after two years of leasing you could have purchased the
tanks outright for the same money. Most leases run from 5-99 years, but if you
move to another area where a different gas company is located, you may be able
to return your tanks to the original location where you leased them and get back
a pro-rated portion, then begin a new lease account in the area you move to.
Look in your local telephone Yellow Pages under "Gasses, Industrial" or "Welding Supplies."
There are usually three sizes of tanks, small (80 cu. ft.), medium (150 cu. ft.)
and large (275 cu. ft.). The small tanks are the easiest to store and maneuver
around the shop and are fine for most occasional users. The medium tanks will
be more than enough for most any home/shop use, lasting more than a year under normal use. The largest tanks are heavy, and more difficult to move around
the shop.

Getting started with
oxy-acetylene
Thoroughly read all the directions that come with your
gas-welding setup before you do anything. If you have purchased a used welding set from someone, make sure the instructions are included, or have an experienced person help
you get set up. Compressed gasses are dangerous; so is the
welding process, and there are many more safety considerations to understand than we can cover here in this book. Obviously, since we are dealing here with a very hot flame and
the promise of flying sparks, you should have a clean work
area away from any flammable materials and a good fire extinguisher should be handy, as well as a source of water. If a
spark gets onto your shoe, don't waste your extinguisher on
that. Use a water spray bottle, which is also handy at times
for cooling off a piece of metal.
Follow your set's directions for attaching the gauge/regulator sets to your filled bottles of oxygen and acetylene (see
illustration). The bottles should be secured with a sturdy

3.19 Most home/shop users of oxy-acetylene will have singlestage regulators on their torch sets. Unless you do a lot of
welding/cutting, these are just fine, though you have to
readjust the output pressure more frequently than
with the professional, two-stage regulators.

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Haynes Welding Manual
chain to either your bench or a welding cart that has provisions to keep it from tipping over easily. Before the regulators
are attached, blow any dust out of the cylinder valves by
cracking them. You should stand to the side of the cylinder
when doing this, with the outlet pointed away, and very
quickly open the valve slightly and close it again. Just a little
blast of gas will ensure that the connection is free of dust.
Use a proper-fitting wrench (not an adjustable) on all
your regulator and gas hose connections, which are usually
brass fittings, and remember that the acetylene connections are left-hand threaded. Blow out the regulator by
slowly opening the cylinder valve when the pressure-adjusting screw (usually T-shaped) is turned out all the way.
One gauge will show you the cylinder pressure, and the
other the hose/torch pressure. Attach the hoses and blow
them out with a blast of gas. Adjust the regulators to provide 2-3 psi working pressure from each bottle (see illus3.20 Gas flow is regulated on the oxygen cylinder to 1 -5 psi
tration). The cylinder valves should always be opened
for welding, depending on the thickness of the material to be
slowly, with your body away from the ends, and the oxygen
welded, and the acetylene pressure is adjusted the same.
Higher pressures are set when performing cutting, but
valve should always be opened all the way. It is of a type
acetylene must never exceed 15 psi to the torch.
that seals best either fully closed or fully open. The acetylene valve should be opened only about 1-1/2 turns.
Connect the hoses to your torch with the gas cylinder valves closed. In most
cases this involves wrenches, but there are some professional sets that have
snap-on connections (like air line hoses) to make quick, wrenchless work of
changing torches (see illustration). Select a medium tip from your set (your set's
instructions will recommend what gas pressure works with which tip and what
thickness of metal they are suited for) and attach to the torch. After everything is
assembled, you can test the connections with soapy water for leaks.
You will need something to light the torch flame, and a wire-framed metal
striker should have been included with your set (see illustration). Never use
open flames such as a cigarette, cigarette lighter or match to start your torch!
Your fingers need to be well out of the way. You should be wearing leather
gloves and heavy clothing with leather shoes or boots. Do not tuck your pants
into your boots, or you could create a pocket there that could collect sparks.
Likewise, do not wear pants with cuffs, for the same reason. Have your colored
welding goggles on your head, but not yet over your eyes.

3.21 Some torches are equipped with quick-release fittings
as usually seen on air-compressor hoses, making
for quick, easy changes.

3-8

3.22 To start a torch, open the acetylene valve 1/2 turn and
light immediately with a striker like this. Never use a match,
cigarette or lighter, you could easily burn your hand. Once
the sooty acetylene is lit, gradually add oxygen until you
achieve a neutral flame.

Gas welding/cutting

Flame adjustment
This is a very important step in gas welding, and one you will be making
every time you pick-up the torch to weld, braze, cut or solder, so you'll have
to practice this to the point where it becomes second nature. Open the cylinder valves slowly as described before, and make sure the regulated pressure
is set correctly. Hold the torch in your operating hand (right, if you are righthanded) and the striker in the opposite hand. Both valves on the torch are
closed. Open the acetylene valve on the torch about a half-turn and operate
the striker near the torch tip. There should be a flame with some sooty flying
particles. Quickly add some oxygen and the soot should disappear. Study the
illustrations of flame type. What you have right now is a carburizing flame,
which is overly-rich in acetylene. As you add more oxygen, the flame characteristics will change. While the rich mix gives you a wide, flared-out yellow
flame, adding oxygen will make the flame narrower and brighter.
The ideal flame for most gas welding is a neutral flame, which is neither
carburizing nor oxidizing (too much oxygen). When you have adjusted the
torch properly, there will be a large flame graduating from blue at the end
away from the tip down to white near the torch and with an inner cone that
should be light blue. If you add too much oxygen, the inner cone will be
smaller, pale in color, and there may be a hissing sound. You'll need to practice achieving the neutral flame, and when you start welding, you'll see what
happens to metals when the flame is incorrect.
The proper method of shutting off the torch is equally important. Close
the acetylene valve on the torch first, then the oxygen. If you do it the other
way around, there could be a small amount of gas left in the tip that could ignite. If you are through welding for some time, it is good safety practice to
then close down the gas cylinder valves as well, but if you are going to weld
again in a short while, just shut off the torch valves only.

Gas welding
You'll need a lot of small pieces of clean scrap metal to practice on, of
varying thicknesses. Even if you only intend to do light sheet-metal welding,
start by practicing with thicknesses up to 1/4-inch to become familiar with
different tip sizes and flame adjustment. The cleaner the scrap pieces, the

OUTER FLAME

Oxidizing Flame
3.23 The oxidizing flame has too much
oxygen, and a feathery blue flame with small
white inner flame. The carburizing flame is
acetylene rich, and features a large flame,
with a large blue inner cone and a longer,
colored cone around that. For welding,
adjust for a neutral flame.

3.24 You don't have to worry about grounding with gas equipment, but
there is a dangerous flame involved, so your welding projects and
practice sessions are best done over some firebricks like this,
which you can get at your welding supply store.

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Haynes Welding Manual
better your welds will be, and this applies to any type of welding, gas or electric.
You should sand or grind the areas to be welded to remove any paint, coatings
or rust. You should not use for testing any metals that are galvanized or coated
with zinc, or any kind of plating. Not only will welding be dirty and difficult, but
the coatings may cause harmful gasses when vaporized in the weld.
Start your first exercise with a piece of steel on a level, non-flammable surface, not a wooden bench. The ideal work area would be a steel table (not just a
wooden bench with thin sheet metal nailed onto it) with some firebricks on top.
The firebricks can be obtained at your welding supply center, and, in addition to
being non-flammable, they do not suck the heat out of your welding sample like a
steel table, and there's no chance you're going to weld the sample to the brick. It
can be very embarrassing when you practice on a steel table and you have various scraps welded - stuck to your table.
With your torch adjusted properly, pull down your goggles and put the torch
tip about one inch from the steel and just try to make a long weld puddle of
molten metal. The torch should be leaning back at a 45-degree angle, with the
flame pointing in the direction the bead is going. When the steel starts melting
into a small pool where you started, move the tip along and give it a rhythmic
motion of an oval shape as you go, trying to follow a straight line, blending the
newly-heated edge of the puddle with the back edge of the puddle. The process
will leave a line of rippled ridges. If you are burning holes in the metal, there may
be too much oxygen, the torch may be too close to the metal, the tip could be
too large or you are possibly advancing the torch too slowly. If you go too fast,
have the torch too far away or the tip is too small, your puddle will be very small
and it won't penetrate the metal very far. The more the torch is pointed straight
down at the metal (no angle) the deeper the penetration will be, and vice-versa.
Practice at different angles until you can make a bead like our illustration, with
even ripples and proper penetration.
Of course, not all of your welding will be done this way, in fact almost all of
your real welding will involve adding filler rod, but for now you need to learn torch
control and rhythm. Many of the projects you encounter will involve welding
along an irregular line, especially in repair work, where you are welding up a
crack. To become more familiar with making a bead along
an irregular line (still without filler rod) draw a zigzag or
curved line on the steel with soapstone and practice making a good bead. Proper hand control is everything in gas
welding. Your hand must be comfortable and steady at all
times. In welding classes, students are often challenged to
write their first name in script with welding bead on a piece
of metal, which challenges you in handling changes in bead
direction.
When you are successful with these experiments laying
down a good bead on the metal, you're ready to try joining
two pieces using a filler rod. This requires not only good
torch control, but control of your other hand as well with the
filler rod. Generally, the filler rod should be the same material as the base or parent metal for good fusion welding. If
you weld aluminum, the filler rod must be aluminum, and
steel rods are used on steel. The steel filler rods are coated
with copper to keep them from rusting and to make cleaner
welds. As a basic rule, select a filler rod that is the same di3.25 Heat in gas welding is controlled by matching the gas
ameter as the thickness of the metal you are welding. Most
flow and tip size to the thickness of material. Your welding
travel speed and tip-to-work distance will control the puddle
light metals are welded with 3/32-inch, 1/16-inch or 1/8size and penetration. With all things right, you should be able
inch rod, and you will probably never gas-weld with anyto heat your first puddle molten in about six seconds, then
thing bigger than 1/4-inch rod. To weld thick materials, sevmove along to make your bead. At left is a bead run too cold
eral passes are required to make a good fusion, and various
(bead stands up), at center is one run too hot and too fast,
forms
of electric welding are usually much faster than a
and at right is a better bead with good width and penetration.
torch at making multiple-pass seams.

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Gas welding/cutting

Welding with filler rod
Let's say that you need to join two pieces of 1/8-inch-thick metal in a straight
bead from right to left. Position the two pieces such that they are butted together
where they are to be joined, and that you have something blocking or clamping
them in place so they won't move as you weld. Start your weld puddle at the
right end of the seam, and as the puddle develops, use your left hand to insert
the tip of the filler rod into the center of the hot puddle, then pull it out right away.
Set up a rhythm of alternately putting in the rod and taking it out as the bead progresses to the left. When we describe the puddle, the edge of the puddle closest
to the direction you are traveling is the front edge, while the part of the puddle
you just finished is the rear.
If you have ever done any soldering, you may have a bad habit of heating the
solder with your torch or soldering iron and letting the molten lead drip onto the
joint. This is a bad habit and one you shouldn't bring with you in your welding
practice. The molten puddle should melt the filler rod, not the torch. If the rod
sticks, then you are not keeping the puddfe molten enough, or you are adding
filler rod too fast, either of which will result in a low-quality weld.
This skill of making a good bead, with evenly overlapping ovals and good
penetration will take considerable practice, but if you learn two-handed gaswelding techniques well, any other welding system you pick up later on will be
considerably easier to learn. Most of the welding you will do will be forehand
welding, in which you angle the torch so that the flame is aimed somewhat toward the direction of the desired weld bead. This preheats the metal as you go
and makes addition of filler rod to the front edge of the puddle easier because it
is truly hot. Sometimes it seems like keeping the proper torch distance, moving
at the right speed, circling or ovaling the tip and dipping the rod in at the right
time is just too much to concentrate on at one time, but you will get the hang of
it. This isn't "brain surgery" and millions have learned before you. After a good
long practice session, begin to examine things around you that are of welded
construction and you'll get an appreciation of the practice it took to lay down
those beautiful beads that look like they were done by some machine instead of
human hands. Indeed there are some kinds of welding that are done with largely
robotic welding machines, but a good weldor can make virtually perfect joints
that are stronger than the parent metal.
We mentioned before that cleanliness is critical in making good welds. The
two edges to be joined need to be sanded or ground clean to bright metal and
should fit as closely as possible. Small gaps are inevitable
in some kinds of work and can be bridged with filler rod, but
gaps should be kept to a minimum. On thicker materials,
you will find that it is easier to make a clean weld with good
penetration if the edges of the two pieces are beveled before you weld. This can be done with a file or grinder. Thin
materials have their own idiosyncrasies, mostly to do with
keeping the two edges in alignment. As you progress with
your weld bead, more and more heat travels out into the
parent metal, so that after welding for some distance, the
metal you now encounter is hotter than the metal you
started on, so you may have to adjust the torch away
slightly to compensate for the puddle forming faster.
Another problem with thin materials is that the parent
metal tends to distort with the application of heat. Metal expands when heated, and two edges that were parallel when
you started welding probably won't stay that way. Usually,
the edges pull away and you have a gap to bridge that was3.26 When practicing basic butt welds, tack the near corner
n't there when you started. The solution is to tack-weld at
first, then tack the top corner with a slight gap between the
intervals before applying too much heat. A tack-weld is
parts. This will close up as the plates grow from welding heat.
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Haynes Welding Manual

3. 27 Start your bead about an inch beyond that first tack,
and proceed toward the end, keeping the torch steady and
dropping molten beads off the filler rod by dipping into the
puddle quickly and evenly as you go, building an
overlapping series of puddles.

3.28 Before you are done, you will notice some movement or
warping of the sample plates. If you plan to do automotive
body work with a torch, you'll have to practice a lot on thin
metal to get the hang of welding without burning holes or
warping the work. Gas welding is not suited to the thin,
high-strength body steels used on today's unibody cars.

simply a bead only one or two puddles long, done quickly. To join a long seam in
sheet metal, tack the ends first, then the middle, and then put tacks every few
inches apart, while alternating the ends you tack (see illustration). When you go
along later to do the final, full seam welding, the tack puddles can be melted into
the main seam as you go, and the pieces will stay aligned the whole way. This is
particularly important when joining long sheet-metal seams like welding a new
quarter-panel onto a car. In auto bodywork, you need to keep the warpage to a
minimum. In some cases when doing the final seam after tacking sheet metal,
you may stop after a few inches are welded and quickly apply a body dolly to the
backside of the weld area and hammer on the weld area on top with a body hammer. This "hammer-welding" (alternating welding and hammering) technique
straightens the seam and the two panels while they are still hot and pliable, and
the resultant seam when done by a good body man requires much less grinding
or filling to make it ready for primer and paint.
The basic joint we have illustrated is a buff joint, where
two pieces of metal are pushed together and welded along
the seam where they meet. There are many kinds of joints,
and it is helpful to try welding a few other types after you
have practiced enough on butt welds on thick and thin materials. Corner welds, where the two edges meet at an angle
can be either inside or outside corners (see illustrations).
The outside corner weld is the easier to perform because you
can see the seam so clearly, and the pieces need not be
beveled. Just placing them so that the edges form a groove
or V will do it. On inside corner welds, depending on the angle involved, the action is harder to observe, being shrouded
somewhat by the pieces. After you have practiced on these
more difficult welds, try a lap weld. This is where the two
pieces lay over each other (overlapping). You run a bead
where the joint is, and depending upon the strength required
for the application, you may want to weld the seam on the
3.29 As you weld, it is inevitable that sparks and spatter will
blow back onto your torch tip. If it plugs up, your bead will be
other side as well. In auto bodywork, sometimes panels have
spotty and your torch may go out entirely. Keep the tips clean
to be overlapped instead of butt-welded, but in such cases
with a set of fine-wire cleaners that come with your gas set.
the backside seam is seldom welded.

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Gas welding/cutting
A T-weld is where you join a piece of metal to another larger piece at right
angles, forming a letter T in profile. This requires some additional practice to perform well, as part of the weld puddle is being made uphill, and the larger piece
may take more heat than the smaller part. You have to play the torch back and
forth over both pieces and get a feel for how much heat each requires.
Further practice sessions for you may involve trying to weld pieces of tubing
and angle-iron together, both typical materials for home/shop projects. Try joining a flat plate to a tube, or making a corner between two pieces of angle-iron.
Careful measurement and cutting will be required to make gapless corners for a
good weld. Square or rectangular tubing is often used in projects such as shop
equipment or a utility trailer, and you should practice making 90-degree corners
from two pieces cut at 45-degree angles. The inside welds will be the tougher
ones, and you'll find when you stop practicing and assemble a real-world project
that you can't always turn the work around to make the seam area flat in front of
you on your bench. Often you will be forced to weld in a vertical seam, or even
weld upside down underneath something. The latter is difficult and dangerous, '
requiring the best in full-face eye protection (a helmet instead of goggles) and a
leather apron over your arms and shoulders to protect you from falling sparks.
Welding an exhaust system under a car, especially if you don't have access to a
lift, can be extra challenging.
When these don't seem like a challenge anymore, you're doing very well,
and you can try making nice-fitting joints between pieces of round tubing. To fit
two pieces of round tubing together, such as in a roll-cage for a race car, requires a measure-twice, cut-once procedure and lots of patience in cutting and
grinding round tubing to join them with full contact. Another procedure to try with
round tubing is to make a slip-fit, with one piece of tubing sized to just fit over
another. In such cases, you can weld around the joint, or, for high-strength applications, cut the outside tube in a "fish mouth," as if it were being joined at a 90degree angle to another piece of round tubing. When this piece is welded onto
the inner tube, the fish mouth makes for a much longer weld seam between the
two and gives greater strength.
Other types of welds you may run across in your projects are spot-welds and
rosette welds. The former is found often in auto sheet metal work, where you join
two pieces of light-gauge material together without welding the seam entirely.
The spot-weld is just a round welding spot, rather than a bead, and is made
when one piece is on top of another and you just melt a puddle that fuses the two
panels together, then move a distance away and make another spot-weld. Filler
rod is often not used in such cases, especially where appearance is more important than strength. Most spot welds lie flat enough that little prep is required to
make them ready for paint. Modern cars are welded with thousands of spotwelds, but these are accomplished by special electric welders, usually computercontrolled and robotic.
Where a little more strength than a simple spot-weld is required, a rosette or
plug-weld can be made. This is where the panel on top has holes drilled or
punched into it at intervals. You weld up the holes, puddling both upper and
lower panels together, which joins them securely in that spot. Plug-welds often
do require some filler rod.
Sometime in your gas-welding work, the torch will go out and you'll get a
loud pop at the torch which will really get your attention because you don't expect it. When welding in tight quarters, you may tend to get the tip too close to
the work, which will overheat the tip and cause a tiny explosion as the gasses
POP inside the tip, which is called a backfire. This will alarm you greatly when it
happens, but the answer is simply to not get so close. You may have been working close to get the pieces hot enough, but if that is the case, you really need a
larger tip or more flow of oxygen and acetylene from the tank regulators to maintain the right heat level with your torch further away from the confinement of the
weld corner. Welding too close to the work will also dirty your tips. So if you have
a backfire, stop work, shut off the gas at the torch and remove the tip for a

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Haynes Welding Manual

3.30 These prevent serious accidents from a flashback,
indicated by a loud squealing noise. Flashbacks are caused
by gasses burning inside the hose. For safety reasons, both
hoses should be equipped with flash arrestors, which are
reverse-flow check valves. Some readjustment of gauge
pressures may be necessary when using check valves.

thorough cleaning. Your welding set will have come with a
set of wire tip cleaners. Cool off the tip with a water-soaked
rag.
Something akin to a torch backfire but much more dangerous is a "flashback." This is where combustion actually
follows the gas trail back into the torch and even the hoses.
At the least there is danger of damaging the regulators and
hoses, but if the combustion reaches the tanks, there is a
possibility of a serious explosion. In a flashback, the torch
goes out and there is a loud squealing or hissing noise with
black smoke coming out of the torch. If this happens, shut
off the oxygen at the torch, then the acetylene at the torch,
then the cylinder valves. Your welding supply center should
have available "flashback flame arrestors" that install in
your two gas lines where the hoses attach to the regulators
(see illustration). Acting like one-way valves, they are designed to prevent serious accidents caused by flashbacks,
and they should be installed on any gas-welding setup,
where the hoses attach to the regulators.
When making welds with filler rods, you will run across
situations where the rod gets short enough for your left
hand to get too close for comfort to the heat of the welding.
Before making a bead, practice will have shown you how
fast the welding rod gets used up and how long a rod you
will need to complete the seam. Start with a rod long
enough to do the whole seam. If the seam is longer and will
take several rods to complete, you will have to stop welding
and get a new filler rod. It will take some time and practice
to get the hang of continuing a bead with a new rod where
you left off before. The trick is to make the whole bead look
like a continuous weld, without little piles of buildup where
you stopped and restarted. When a rod gets short, many
welders simply tack the short piece onto the end of a new
rod and go right on welding. When you get good at it, the
bead won't have a chance to cool off too much. In insidecorner welding, you may want to take the welding rod and
put a bend into it, such that it puts your hand in a more
comfortable position, further away from the heat of the action (see illustration).

Checking your welds
Chances are, you won't be making nuclear-vessel welds in your home/shop,
or other welds so critical that they require X-ray inspection to pass specifications,
as is often done in commercial welding. However, you do want to learn how to
make strong joints, and your practice time should include some testing as well.
Looks are important, but a good-looking bead may not be a proper weld, especially if it doesn't have good penetration. Checking for good penetration requires
looking closely at the backside of the welded joint, which is easy for you to do
with your practice sample pieces. In real-world situations, it isn't always practical
to get at the backside of something you have welded (like a joint between two
rectangular or round tubes), so you should be familiar with the proper heat control and penetration before you consider yourself through with your practice
phase.
In looking at the back of the weld, see if there is any buildup on the backside.
A small amount of "dropthrough" is acceptable, but 100% penetration can be

3-14

Gas welding/cutting

3.31 After you have gained some welding experience, and a good torch weldor isn't trained in one day, you will learn to read the
welding conditions based on the flame from the torch. This troubleshooting chart indicates some of the causes and
cures of torch flame problems.

achieved without extra material building up on the backside. Good penetration is
particularly important in welding auto body panels, because the outside of the
weld bead is probably going to be ground down with a body grinder in preparation for filling and painting. Thus the strength of the topside buildup or puddling
will be gone and the joint's strength will rely totally on the fusion of the two
pieces below the surface. In your tests of practice welds, it can be helpful to use
a hacksaw to cut through the center of one of your welded joints to see just what
the penetration is. You can't always tell by looking at the ends of the joints, because of how you may have ended the bead.
We're assuming that your home/shop has a good, sturdy bench vise. It can
be useful in testing your welded joints. Your first practice welds may have been

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Haynes Welding Manual
straight seams with two pieces butt-welded together. Take your best example
and put it in your vise with the weld seam close to the jaws (see illustration).
Clamp a pair of vise-grip pliers on one edge of the upper piece and start hitting
the upper piece with a hammer, while holding it with the pliers so it can't fly off.
Hammer the upper piece until it's bent over all the way onto the vise (making a
90-degree angle in the welded pieces). Remove the sample from the vise and examine the weld. If the upper piece broke off during hammering, it obviously wasn't a strong enough weld.
Any of the various joints you may have practiced on can be tested by hammering. Whatever the joint, just secure the piece and hammer on one of the two
joined pieces. Hammer from the backside area of the joint and toward the side
that you welded on. If good penetration wasn't achieved, the backside will be
weaker than the front and bending the metal this direction will really test the
backside for good fusion. Even a weld with 100% penetration may not be strong
enough if there was any "undercutting" on the top side. Undercutting is a groove
along either or both sides of a bead, caused by applying too much heat or holding the torch at the wrong angle. In a stressed situation, the undercut area will be
the weak point and the joint may fracture right along the undercut area.

Brazing
Brazing, or braze-welding, is not a true fusion process
such as we have been discussing. The parent metal does
not melt into a puddle. The parent metal is heated and the
brazing rod melts into the joint securing the two pieces together. The brazing rod is made of brass (an alloy of copper
and zinc) and is used in conjunction with a flux, which may
come already on the rod, or in a can that you dip the rod
into to coat it as you go. Brazed joints are as strong as
welded joints when done properly and with an overlap of
the pieces, but brazing is particularly helpful where the
higher heat of fusion welding would harm the parent metal
or adjacent materials, or where the pieces being joined are
made of brass or copper.
The rod material melts at a much lower temperature
than the parent metal, so the basic principle is to heat the
3.32 Brazing with a gas torch has many uses, such as
repairing castings and antique-car sheet metal. Here a fluxparent metal just above the melting temperature of the filler
coated rod is being used. Brazing is not a fusion process,
rod, so that the parent metal, not the torch, melts the rod.
so it is used where higher, melting-point heat might
Overheating the rod with the torch will boil the zinc out of
damage the work, or surrounding materials.
the rod and cause poor adhesion in the joint. Brazing is
most often done where there is an overlap of two pieces, or
in building up a worn or broken area of a casting, that will be re-machined to
original shape after brazing.
A joint to be brazed must be thoroughly cleaned, by grinding, filing, or sanding. When you have selected the proper rod for the material you are working on
(copper/zinc for ferrous metals), you begin by heating the joint with your torch,
using a lot less heat that you would for welding. You should pull the torch tip
back 2-3 inches, which is much further back than with gas-welding. When the
metal is dull red, apply the filler rod to the hot spot on the parent metal and see if
it melts in. Heat next to that spot and apply some more fluxed rod, keeping this
process going until you have completed your seam. When a long seam is contemplated with brazing, preheat the whole area. When the metal is the correct
temperature, the brazing rod will flow nicely into the joint; if the metal is too cold,
the braze material will ball up on the surface, and if it is too hot, it will spread out
over a wide area. White smoke during the process usually indicates the area is
overheated, and the smoke is the zinc boiling off. Not only does this affect the
quality of the joint, but the fumes can make you sick if you breathe enough of
3-16

Gas welding/cutting
them. Even if you don't overheat the rod, there are fumes
given off during brazing.
Always braze with adequate ventilation, and a good
respirator mask is also helpful insurance. Brazing is often
used when joining pieces of galvanized metal because it
will adhere better than standard gas-welding; however, this
combination of brazing fumes and fumes from the plating or
galvanizing should be avoided unless you are outdoors.
If you are familiar with basic soldering, you know that
good adhesion is ensured by using flux, a compound that
prepares the metal for a strong bond, and you may also be
familiar with the term tinning. Tinning is a process (in soldering) of applying a thin coating of lead to the fluxed surface
before the main solder is melted in. The procedure is similar
in braze-welding, except that, when brazing thin materials,
the tinning usually takes place as you are brazing, in one
step rather than two. Brazing larger joints requires that a
3.33 Most welders use dip-type powdered flux for
light coating of brass be flowed onto the surfaces, making it
convenience, since the pre-coated rods can flake if they
easier for the main brazing to stick to. The flux for brazing
are exposed to moisture. Plain brazing rod is heated with
the torch, then dipped into can of flux and pulled out coated
can be a part of the rod itself (pre-fluxed rods) which is conwith enough flux for an inch or two of brazing travel.
venient, or you may have a metal can of flux on your welding
table. You simply heat the end of your brazing rod and stick
it into the flux and withdraw it covered with flux (see illustration). Once you have
started the brazing process, the rod will always be hot enough to pick up flux as
you need more. The pre-fluxed rods are convenient, but the coating is somewhat
fragile and won't take rough handling. These rods must also be kept very dry.
When brazing thin sheet metal, the purchase area or overlap between the
two panels is the key to the strength of the joint. When there is 3/4-inch or more
of overlap for the brazing to adhere to, the joint will actually be stronger than the
parent metal. Because the brazing rod melts at only about 1000° F instead of the
steel's melting point of 2700° F, brazing will induce much less warpage in thin
metal, which is why it has been used for years in many areas of traditional autobody repair. The overlap in the brazed joint also makes the joint area much stiffer
(two thicknesses of metal there), so a seam such as when installing a body patch
panel will take less hammer-and-dolly work to prepare for painting (see illustration). Brazing will not work on a butt-joint because there isn't enough "captured"

3.34 Lap welds are best for brazing, such as when joining
overlapping sheet metal panels where the brass has lots of
contact area for adhesion. As with fusion welding, tack the
ends before running the whole seam.

3.35 You should start with very clean metal when brazing,
although the flux is designed to surface clean as you go,
leaving some minor slag afterwards. You will have to keep
the torch further away from the seam than with welding,
to keep from overheating the brass.

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Haynes Welding Manual

3.36 End view of a brazed lap joint, showing how the brass
flows in between the plates with capillary action, much as
solder does when applied to a hot copper pipe. The base
metal must be heated to the point where it melts
the rod, not the torch.

3.37 There is some silicon slag after brazing (arrows), which
can be softened with water after the part cools enough so
that water will not warp it, then the rest comes clean
with wire-brushing.

area for the capillary action to flow the brass into each piece, although you can
back up a butt-joint with a strip of similar material, which gives an overlap on
both pieces and good bonding area for the brazing.
Although brazing is still a technique used by older body craftsmen in restoration of antique and collectible cars, it should not be used on new cars that are
built of low-alloy, high-strength but lightweight steels. In fact, some car manufacturers specify that no torch work at all should be done on their body metal, that
only MIG welding is acceptable because of the narrow heated area and faster
welding-bread travel.
Other metals than steel can be brazed as well, such as stainless-steel, castings, brass, bronze and even aluminum when a special aluminum-brazing rod is
used. If you have special project considerations or a question, ask your local
welding supply for advice on choosing the best brazing rod
for the job. One advantage of brazing is that dissimilar metals can be joined, which ordinarily can't be done with fusion
welding. Also, where two pieces of different thickness are
being joined, like a thin pipe to a thick flange, brazing is
preferred. In ordinary gas welding, you have to be very
good with the torch to play the right amount of heat onto
the thicker piece while not burning up the thin piece. With
brazing, neither piece needs to be heated beyond the melting point of the brazing rod.
After braze-welding a seam, you will see that the flux
remains as a kind of crust on the parent metal. It should be
removed with a wire brush, and can be softened with water
first, which makes the wire-brushing work easier.

3.38 The versatility of gas welding equipment has always
found favor in the exhaust system business. You must be
careful not to cut or weld near fuel tanks, fuel lines,
electrical components or brake lines, but the equipment is
highly portable, and can cut as well as weld. Long welding
rod can be bent to curve around exhaust pipes to weld in
tight quarters.

3-18

Oxy-acetylene
cutting
The other side of the dual-purpose nature of gas equipment is the ability to cut as well as join metals. The gas
torch can make short work of cutting through even large or

Gas welding/cutting

3.39 Muffler installers also find uses for welding rod to simulate the
length and required bends for a pipe to be installed. Bent wire is taken
over to the hydraulic tube bender where shape is duplicated in pipe.

3.40 Sometimes, the oxy-acetylene cutting torch
the fastest, easiest way to remove the old
exhaust system.

thick pieces of steel. For sheet metal work you will probably continue to use shears and other hand tools to cut
light-gauge material, but being faced with cutting through
a half-inch steel plate with a hacksaw will easily convince
you of the value of a cutting torch.
The only oxy-acetylene cutting component different
from your basic wefding setup is the torch itself. The cutting torch has one major difference from the welding
torch: it has an extra oxygen supply, operated by a lever
instead of a valve (see illustration). Actually, when you
cut steel with a torch, it isn't the flame that is really doing
the cutting; it is a strong flow of oxygen that hits a heated
part and the oxidation of the metal happens so fast the
affected area disintegrates into flying sparks. The basic
principle of oxy-acetylene cutting is that the torch tip has
several small holes surrounding a central larger hole. The
3.41 The cutting torch is adjusted for a good flame, then
smaller outside holes are where the basic oxy-acetylene
checked with the extra-oxygen supplied when the cutting
flame comes out - actually several small flames. These
lever is depressed. The flame should remain close to
neutral. The excess oxygen is what is used to
flames are really used to preheat the metal to be cut. The
push the molten slag from the kerf as you cut.
weldor adjusts the gas and oxygen flow on the torch for
the proper flames from the pre-heat holes and plays the
torch on the end of the piece to be cut. When the end is heated to a cherry red
color, the weldor presses down on the cutting lever, which activates a strong
flow of pure oxygen through the large central hole in the tip. This is the oxygen
that really cuts through the metal.
Because oxy-acetylene cutting involves a huge shower of sparks from the
underside of the metal you're cutting, you must be prepared before cutting. Clear
the area around your welding table, have the proper welding attire on (including
leather welding gloves), and make sure the area under the test piece is clear of
any obstructions. It's best to support your test piece on some firebrick, leaving
the area under the cut line open. If there were any restriction to the flow of sparks
under your test piece, molten shrapnel could blow back into the weldor's face.

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Haynes Welding Manual

3.42 As in welding, the flame of your
cutting torch head should be adjusted
to a neutral flame before cutting.

Mark your cut line using a sharpened piece of soapstone and a straightedge.
After marking the cut line, find a piece of tubing or angle-iron that you can clamp
down onto the workpiece to act as a guide for the torch head (see illustration).
Before you begin cutting with your oxy-acetylene torch, you should reset the
regulators. Adjust the acetylene gas to 2-3 psi, and the oxygen to 15-20 psi,
since a much larger percentage of oxygen will be used in the process. Select a
gas pressure and tip size that correlates to the thickness of the material you are
cutting. Your setup's instructions will tell you the recommended sizes for that
brand of equipment. Light your torch as you have learned to do in gas welding
practice and watch for a neutral flame from the preheat holes in the tip. Watching
the flame pattern, try cutting in the extra oxygen flow from the cutting handle. It
shouldn't affect the quality of the preheat flames. Place the torch flame at
the edge of the material you want to cut and hold it there a short distance from
the material (1/16-inch or 1/8-inch away). When the metal is cherry red (about
1500° F), angle the torch tip back about 10 degrees (with the tip aiming in the direction of the cut) and cut in the oxygen. You'll find that oxy-acetylene cutting is
much easier to learn than the welding process was; the main thing to learn here
is the proper travel speed for the tip size, gas pressure and metal thickness you
are working with.
When you cut through metal with the torch, the quality of the cut edges will
tell you much about the process. At the bottom edges of the cut, slag may collect, leaving a rough edge that must be cleaned up with a grinder later. Also, remember when you are cutting that the torch takes out material as it goes; the
part being removed is called the kerf. When you draw soapstone lines to cut out
shapes, remember to cut outside your lines, or the part will wind up being too
small. After your have experimented a little with the torch, you'll have an idea of
how big the kerf will be with certain tips and certain materials.
If you try to advance the torch too fast, the bottom of the kerf may
be irregular or not cut through all the way. When you look at the edge of
the cut metal, you'll see vertical lines in the edge of the cut, in a good
cut these lines are straight and smooth, in a rough cut the lines are almost like teeth on a saw blade. If you advance the torch too fast, the
cutting lines will look curved back toward the direction you started the
cut from, instead of straight up and down (see illustration). If you
move too slowly with the torch, the top of the kerf will be rounded off,
and the bottom edge may accumulate too much slag. If you have
someone else in the shop with you, have them observe your cutting
from a safe distance. When you are making good cuts, the shower of

Cutting Thin Panel
3.43 The cutting torch should be held more
nearly vertical to the work when cutting heavier
metals, and angled back when cutting thinner
material like exhaust pipe or sheet metal.
Use scrap steel tubing or angle as a brace
to guide the torch for steadier cutting.

3-20

3.44 Examine the cut edge of plates after you have used your cutting
torch. The proper heat and travel speed is when there is the least
amount of slag along the bottom of the cut. This hand-held cut
was moved a little too fast, as evidenced by the angled cut lines.

Gas welding/cutting
sparks should come straight down to the floor. Your
observer can tell you if the spark flow is going back
toward the beginning of the cut, which indicates that
the metal isn't being cut all the way until after the
torch has moved on, the result is that the uncut area
at the bottom directs the sparks back toward the beginning of the cut. Some of the sparks and blobs
could also get blown back into your face or clothing,
so learn to develop the right cutting speed for clean
cuts.
You will find that the steadier you are with the cutting torch, the better the cuts will be, and half the
problem of cutting is finding a comfortable position for
your hands. Since only one hand is required to operate a cutting torch, you can use your other hand
(gloved) to steady the torch and help advance it correctly along your cut line. Keeping the torch tip the
same right distance from the work is also important,
so find a piece of angle-iron or tubing in your shop
sized such that, when you rest your torch neck on it, it
3.45 Clamp a piece of metal to your work that spaces the cutting
puts the tip about the right distance away from a
torch head just the right distance to make your cut-line. The steadier
piece of steel the angle or tube is lying on (see illusyour torch is held, the cleaner the cut. Travel at a very steady speed.
tration). Mark and save this piece as your torch rest
and it will be invaluable in making straight, clean cuts.
There are many methods for cutting steel for projects, like saws
and abrasive discs, but the versatility of the cutting torch is that you
can cut out a piece of one-inch plate in the shape of an elephant if you
want to. Irregular shapes cut out just as easily as straight lines, as far
as the torch part goes, though you will have to develop a rhythm of
smooth hand movements with the torch to follow your soapstone lines
accurately. As with any aspect of welding, this will take practice. You
can also stack several pieces of plate together. Either clamp them together or tack-weld the edges, and when you cut (sizing the tip for the
combined thickness) you can cut out as many as a dozen identical
pieces. To keep them truly identical if necessary, these parts can later
be tack-welded, clamped or bolted together for the final sanding or
grinding of the edges, ensuring that they all match in dimensions.
Besides making straight cuts, which are easiest, you may find that
some projects require certain shapes to be cut out more than once.
Here is where various cutting aids can be used. If you can make the
torch tip follow a pattern of some kind, you can cut out the same
shape repeatedly. Perhaps you need four round discs of steel six
inches in diameter. You can make a steel or wooden pattern that has a
circle in it bigger than six inches. How much bigger than the six-inch
measurement depends on the size of the kerf with the tip you are using. If you know that you need an extra 3/8-inch to allow for the kerf,
make a template with a hole 3/8-inch bigger all around. When you use
this as a cutting guide/rest for the torch, you can cut out as many circles as you want and they will all be round and the same size. You
clamp the template over your workpiece and move the torch around
your cut, always in contact with you template. The smoother your template and the steadier your hand movement, the nicer the cut will be.
3.46 A tool you will see in most race car, hot rod
Watching a pro weldor some time will show you how perfect you can
and fabrication shops is a mechanized cutting
get with what seems like a relatively-crude method of making a part.
torch, often called a flamecutter. It uses a motorIn fabrication shops, special equipment is used to make repeated
driven torch to travel around a template and cut
cutout shapes where lots of parts are needed. One of the basic maout exact shapes. Templates can be temporary
chines you would see in most street rod or race-car shops is a "flameones cut from heavy cardboard, to steel
cutter" (see illustration). This is basically a cutting table on which is
templates for frequent use.

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Haynes Welding Manual

3.47 This mechanized cutting setup from Daytona MIG uses a
standard cutting torch, laid down and clamped in place.

3.48 The complete Daytona MIG shape-cutting table is shown
here with the erasable porcelain layout table folded up to take
up less space when not being used. This table can be used
with a gas torch or plasma cutter.

mounted a framework that holds a special torch, with a straight cutting end instead of a 90-degree end like most hand torches (see illustration). There is a series of arms that allow the torch to stay perfectly vertical and yet move to follow
any shape on the table, and at the top is a small electric motor. There is a place
at the top to mount a template, usually made of heavy-gauge sheet metal, and a
magnetized, knurled tip on top of the torch assembly that follows the template
exactly. The motor drives the knurled tip around the template at a steady speed
(adjustable for the thickness of the material being cut), while below, the torch tip
cuts out exactly the shape of the template. Removing the human element
from the torch movement means that a flamecutter can make smoother,
more repeatable parts. In most shops with a flamecutter, there is usually a
large wall behind it on which hang a wide variety of templates for frequently used shapes, such as suspension brackets (see illustration). In
some shops, the flamecutting setup has a pantograph arrangement, which
is a series of arms that make the torch cut out a shape dictated by the
movement of a stylus around a template on a table next to the flamecutter.
Some sophisticated machines have an electronic stylus that will follow the
lines of a blueprint or even the lead of a pencil line drawn on paper.

3.49 Wherever you find a flamecutter, chances
are you'll find a wall of metal templates
nearby, used to easily and precisely duplicate
commonly used shapes such as suspension
mounting brackets. At lower left is a shape
used to make a head for an engine stand.

3-22

3.50 Most mechanized cutters have a drive head with a magnetized tip for
following metal templates, inside or outside a pattern. The cutting
speed is infinitely variable to suit the material.

Gas welding/cutting

3.51 The ESAB Porta-Graph can be moved anywhere you
have a source of electricity, and is useful for cutting
shapes out of large steel plates that won't fit
under a stationary cutting machine.

3.52 This flamecutter with swing arms can be mounted over a
plate, or bolted to a table.

If you decide to cut out shapes with your oxy-acetylene
torch, you will probably need to build a cutting table (see illustration). On a straight cut, the end of the part can be laid
over the edge of your bench; the work is supported and the
cutoff piece just falls to the floor. But cutting out shapes
larger than a few inches means you need a different surface
to work on, or you'll soon be cutting into your bench! Look
at the photos of some of the cutting tables pictured and
you'll see how to construct one. A framework is made that
holds long strips of 1/4-inch steel straps in an edge-up position, spaced an inch or two apart. The framework should
be placed over some kind of fireproof container, like an old
drum (sandblasted clean of any flammable residues first).
This will capture the flying sparks and hot scrap pieces and
keep the shop neater and safer. Another safety consideration to watch for is protection of your feet. Make sure when
you are cutting out a heavy part that it isn't going to fall
right on your feet. Either have a metal deflector under your
cutting area, or keep your feet well away from where the
3.53 Under a mechanized cutter, you need a grate like this to
support the work while it is being cut. After some usage, the
very hot part is going to fall.
1/4-inch by two-inch slats will be fairly cut up, but can be
There will be times when you cannot start a cut at the
pulled out and swapped end for end, top for bottom
outside edge of your workpiece, and you will have to cut
or simple replaced.
from inside a pattern. This requires a little different technique to get the cut started. Adjust the torch to a neutral
flame with the cutting lever depressed. With the lever off, start heating a spot on
your workpiece along the cut-line. When the molten puddle starts to appear, pull
the tip back about a half-inch (because this is a closed spot, there is a chance of
molten metal and spark being driven back into the tip if it is too close) and slowly
cut in the cutting lever. When the spot becomes a complete hole, you can proceed around the rest of your pattern or line.
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Haynes Welding Manual
Some parts cut with a torch need to have a beveled edge if they are going to
be joined with another part by welding, such as when joining sections of heavy
pipe. Cutting a beveled edge on a round pipe by hand is challenging, and in the
pipe-fitting industry they often use a machine that clamps around the pipe. The
fixture holds a cutting torch, and a motor drives the assembly around the pipe
smoothly and evenly, and is adjustable for speed and the angle of the bevel.
There's no place for such equipment anywhere but in the pipe business, but it's
interesting to see the ways in which the human element of hand control of the
torch can be eliminated with special equipment. When you do make beveled cuts
in thicker metals with your torch, you should remember to size the torch tip to the
measurement across the bevel, which is thicker than the straight thickness of the
metal.

Heating with
oxy-acetylene

3.54 The rosebud tip will be useful for heating metal parts to
be bent, freeing press-fitted parts, and for preheating
castings before welding, such as here where a cast-aluminum
mailbox post is preheated before TIG welding.

3.55 A great aid to cutting straight lines manually is this
"compass" guide. It holds the torch tip firmly, but in a swivel
arrangement that allows it to turn as you move along the line,
and the torch stays the same distance from the work and
much steadier. Here it is being demonstrated against another
great tool, a magnetic steel guide that sticks strongly
to the work and saves the hassles of setting up a bar
or tube with some clamps.

3-24

You will be surprised how easily a piece of heavy steel
can be bent into a shape when it is properly heated with a
torch. Even a thick piece of steel, heated to a cherry red
color, can be bent like a sheet of soft copper. Your bench
vise will come in very handy for projects like this. The oldtime blacksmiths hand-shaped everything they made the
same way, except that they had to heat the part in a coal or
wood fire, while you can do the same thing in seconds with
an oxy-acetylene torch.
Depending on the thickness of the metal and the area
to be heated and bent, you can use a welding torch or cutting torch to heat up the workpiece. It shouldn't take too
long to get the area cherry red; if it does, use a larger tip on
the torch. There is another type of tip that can be used
called a rosebud, that is expressly designed for heating. If
your oxy-acetylene set was a deluxe model, such a tip may
have been included, or you can easily get one at your welding supply center.
The rosebud tip has a much larger end that flows a
huge amount of gas. You will have to crank your tank regulators up to perhaps 25 psi on oxygen and 10 psi for acetylene to feed this device (never exceed 15 psi on the acetylene regulator). The big, wide flame of the rosebud tip is
ideal for spreading heat, and lots of it, more evenly around
a part than with the tighter flame of a welding or cutting
torch tip, although those can be used to heat small areas,
especially if you are just freeing frozen, rusted fasteners.
The most common usage of the rosebud tip is for heating components that are press-fitted together. Heat expands metal, so logically, if you can heat up the exterior
part while not heating the interior part, the heated part will
expand and can be removed (with tongs). This is most
commonly done in automotive or industrial situations where
there is a gear pressed on a shaft, or an axle bearing must
be removed. In some situations, however, you cannot simply blast the area with uncontrolled heat, or damage may
occur to one of the components. You need to apply only as
much heat as it will take to separate the parts, no more.
Your welding supply shop should have a variety of paintmarking sticks or crayons that are designed to melt or

Gas welding/cutting
change color at specific temperatures. One brand, called
Thermomelt, is available in 87 different temperature ratings,
from 100° F to 2200° F, and in a liquid, stick or pellet form.
You use this product on the part you need to protect, and
only heat the area until the product melts or changes color,
then you work on separating the components without
adding any unnecessary heat. These products are also useful when tempering or retempering tools that have been reground, which is a lengthy subject unto itself.
Deciding which type of welding equipment to buy is always a tough decision, but one that is made easiest by
carefully defining your needs before buying any equipment.
When you have read all the chapters in this book, you
should have a good idea what the benefits and drawbacks
of each system are, and what is best-suited for your work.
Any weldor will tell you that the versatility of the gas-welding/cutting setup becomes valuable when you need it. Even
when most of your work is done with some sort of electricwelding equipment, you'll find so many handy uses for oxyacetylene equipment that if your budget can handle it and
you have enough work to utilize it, a great idea is to have
the gas equipment and some form of electric welder, too.

3.56 The same tool can be used, with different attachments,
to cut a perfect circle of any size from a few inches to two
feet in diameter. Removing as much of the human element
of hand control makes for better parts that require
less grinding to finish.

3-25

Haynes Welding Manual
Notes

3-26

Arc welding
One of the oldest forms of welding, arc or "stick" welding offers versatility, strength and the ability to handle big
projects and thick materials. Also, introductory equipment
can be purchased inexpensively. There are some rather expensive arc-welding machines, but the most common ACcurrent machines will do fine for the home/shop user doing
standard projects and repairs.
If you have thoroughly read Chapter 2, you should have
a good understanding of the various kinds of welding
equipment and what each type is capable of. If you think
the arc welder serves your needs, then this chapter will give
you a basic introduction to the equipment and procedures
involved. When shopping for a machine, you may see them
referred to as SMAW welders, which is the technical description of the process and stands for Shielded Metal Arc
Welding.
Basic-yet-rugged arc machines are available today in
welding equipment stores, major nationwide stores such as
Sears and Montgomery Ward (and their mail-order catalogs) and can sometimes be found at a good savings in
large lumber/home supply centers that carry a lot of power
tools. Most starter units are sold with a complete setup, including welding gloves, helmet, chipping hammer, sample
electrodes, and a basic instruction book. Other than the
consumable welding rods, there will be little else you will
ever have to buy to continue arc-welding.

4.1 Arc welding will always be with us, as the best welding
method for joining heavy plates for commercial, farm and
industrial work. The weldor requires considerable protection
from the spatter and radiation, usually wearing heavy leather
protective gear.

4-1

Haynes Welding Manual

4.2 For home and farm use, the
Lincoln 225 is the classic AC buzz-box
welder, having been in production
relatively unchanged for decades.
Most home/shop units are AC only,
and require some rewiring to
accommodate the required
220V input.

4.3 Another popular AC 220V welding machine for non-industrial use is this
Miller Thunderbolt 225. The crank handle on top changes the output
amperage, which is read on a scale at the top left of the front panel.

You can find arc machines priced from less than $200 to professional units
costing several thousands, depending on the features, but most home/shop projects and farm repairs can be performed with machines at the lower-priced end
of the spectrum. There are really no moving parts involved in the machinery, and
most of the name-brand equipment is rugged enough to last for many years of
service. The larger machines offer certain advantages for application in professional shop use only, such as higher amperage, AC/DC switching and higher
duty-cycles.
The principle of arc-welding is to attach a ground cable to the workpiece, set
the machine for the correct amperage based on the thickness of the material, fit a
consumable electrode (welding rod) in the electrode holder, and with your helmet
down strike the rod against the work to start a flow of current, the arc, that produces intense heat and light and welds your seam together. Welding thicker materials requires more heat in the form of higher amperage from the machine. The
basic arc machines of interest to you generally have an amperage range of 40-225 amps. The arc process is best suited for
thicker materials, but you will probably never use your machine
at the higher settings. Even when welding on materials oneinch thick (which you will most likely never encounter in your
home shop), or when repairing large castings, the seam isn't
completed all in one big bead, it requires several passes on
overlapping beads to totally join the parts.
At the same time, you will probably never use your AC
welder at the lowest settings. For materials thinner than 1/8inch, there are other welding processes more suitable, such as
gas, heli-arc or MIG-welding. Most of the basic welding per4.4 The layout of the arc-welding setup is simplicity itself.
formed with AC arc-welding machines is done at 90-125 amps,
The rod (also called a stick, stinger or electrode) is both
on materials from 1/8-inch to 3/8-inch and sometimes 1/2the source of the arc and the shielding gas, produced
inch.
as the rod melts its flux coating.
4-2

Arc welding

Comparing duty
cycles
What you will look for in an arc machine,
therefore, is not the highest amperage it offers, but
the duty-cycle at the 90-125-amp ranges you will
use most often. We discussed the duty-cycle in
chapter 2, but it bears repeating in brief. All electric welding machines have a duty-cycle rating,
which refers to how long they can weld at a specific output without overheating. The duty cycle is
described as a percentage. If a machine has a
100% duty cycle, it means that it can be operated
virtually all day, except to stop when you change
electrodes. The percentage is actually based on a
ten-minute period as a test, meaning that if the
duty-cycle was 50%, the machine could be used
for five minutes out of ten. You could weld non4.5 Virtually any building over single-family-home size requires
stop for five minutes and then "rest" the machine
structural steel in its construction, and that requires arc welding. Here
for five before starting again.
a large beam is being prepared for earthquake retrofit
The duty-cycle rating confuses most first-time
in a public school.
buyers, because different companies may take
their published ratings from different amperage
settings. The higher the amperage you weld at (for thicker material),
the less the duty cycle will be. Obviously, the machine will overheat
quicker at the higher amperages. On every machine's range of amperages, there is probably a point where the duty cycle is 100%. A
specific machine may have a 50% duty cycle at its highest setting,
yet have a 100% rating at the mid-range settings you will use most.
It's important when shopping for a welder to find out what the ratings
are for the high range and the mid-range. In the larger professional
machines designed for welding shops and production-line work, the
duty cycle must be close to 100% for any situation, and thus these
machines have to be built with much more expensive components
and reserve capacity.
Some of the duty-cycle rating comparisons may be academic for
the average home/shop user. If the only long seams you weld are on
thin materials at lower heat settings, most machines will be fine for
your purposes, and there is no reason to spend many times more for
the machine to get a higher duty rating. In a typical home/farm project, say where you are welding together steel tubing to make a utility
trailer, the setup of the work takes half or more of your time anyway.
Each welded joint between pieces of tubing may only take one or two
minutes of actual welding, and then it may take you four minutes or
more longer to set up clamps on the next joint or flip the work over
before you're ready to make another weld. The point is that, in this
example, a welding machine with a 40% duty-cycle at the amperage
4.6 In industrial use, the arc welding is generally all
you were using would be perfectly adequate for the job. You wouldn't
DC, and you will see these venerable Lincoln
welders performing their duties day in and day out
find yourself being slowed down on the job because you had to weld
for years. Most industrial machines have a 100%
and then wait for the machine to "catch up." However, there is someduty-cycle for production work. This one is housed
thing to be said for having some duty-cycle "cushion," and if you
outside in a steelyard, enclosed in a
were considering two machines in the same price range and featured
weatherproof box.
similarly, you would take the one with a higher duty-cycle at the heat
you would most often use it. Generally, the machine with the higher
duty-cycle at a mid-point amperage will also have higher ratings at
other settings.
4-3

Haynes Welding Manual

AC, DC or both?
Most of the basic machines in stick welding
are AC-powered. For those readers who may
have taken electricity for granted since highschool physics classes, AC refers to alternating
current, which is what we have in our houses,
businesses, and power lines. The DC designation
refers to direct current, for which the most common daily usage is in the 12-volt systems in our
cars. When electricity was first being used in the
1890s, Thomas Edison, for all his genius in other
scientific regards, was insistent on DC current
being the standard for home lighting and any
other usage. Unfortunately, DC current isn't practical to send any long distance through wires, and
with DC every neighborhood would have to have
their own power plant. The brilliant Nikola Tesla
(the true inventor of the radio and many other
breakthroughs) developed the alternating-current
system and licensed it to Westinghouse, which
became a giant corporation when AC was accepted as the world standard (AC could be sent
hundreds of miles along power lines).
How AC "alternates" is by traveling in a wave,
alternating in polarity up and down in a repeating
4.7 In larger welding shops, a more sophisticated power source is used,
such as this 300-amp Miller DC machine, which has a few more "bells
cycle. Most electricity in the US alternates at a
and whistles" than the home-type units.
rate of 60 cycles-per-second. What all of this
means to arc-welding is that the less-expensive
arc-welding machines are AC-only. The AC
welder is very good at producing less welding spatter, at welding heavy plates
with large electrodes, requires less electricity to run and usually has less maintenance expense than bigger machines. They take the standard line current, which
is high voltage but low in amperage and reduce it through a transformer to a lowvoltage/high amperage current for welding. The only drawback to AC arc-welding is that the constant switching of polarity can make for tiny inconsistencies in
the weld bead, imperfections you and I would never notice, but something that
could be critical in an oil field pipe line, high-rise-building framework or a nuclear
reactor. For this reason, most professional arc welders are DC, which produces a
much smoother weld, a more stable arc and there is a wider selection of special
electrodes (rods) for the DC-type professional arc welder. The AC-only machines
are generally used strictly for joining ferrous metals, but the DC machines can
also be used for stainless-steel and for hard-surfacing industrial parts. In addition
to the two current-specific types of arc welders, there are also combination
AC/DC machines, which usually have a rectifier added to a basic AC machine.
Another factor separating the larger professional machines in terms of flexibility is the choice of polarity, and the option of a TIG torch setup. In the DC
mode of operation, the operator of some machines can choose between negative or positive polarity, depending on the type of metal he is welding and the rod
he is using. Most DC welding is done with reverse polarity, meaning that the rod
is positive, and the work clamp is negative. This method keeps the rod very hot
and makes for smooth welds and improved out-of-position work (anything other
than flat on your welding table). This is not of concern in using AC machines because the nature of the current is switching polarity 60 times a second anyway.
Many of the professional machines are versatile power supplies that can perform
arc welding, MIG-welding (with the addition of a motorized wire-feeding attachment), or TIG-welding with an optional torch and foot control (see illustrations).

4-4

Arc welding
This is the kind of equipment you will find in professional welding/fabricating shops, but most
shops today don't perform much arc welding, using their power supplies mostly for TIG welding,
and using a separate machine for most wire-feed
requirements. The arc-welding arena in professional welding is usually in industrial jobs or construction, pipelines, etc.
Not to confuse you any further about electricity, but the larger professional machines are often
available for several types of input. The most basic machines, home or shop, require 220V, and
industrial units may be set up for 440V or more,
and there are different phases as well. The type of
current we have in most homes is called singlephase. The larger professional arc welders are
made in three-phase configuration, which simply
means that there are three identical inputs
spaced 120 electrical degrees apart. The waves
in these inputs overlap, so that voltage never falls
completely to zero, making for smoother welds.
Many industrial shops have big motors on lathes,
mills and other machinery that run on three-phase
power, which is smoother and cheaper to operate
on large equipment. We will not find three-phase
power at home, and some expensive equipment
is required to set up a building for industrial threephase power.

4.8 Many shops utilize a "power source" machine which not only
powers arc welding work, but can be set up to take a TIG torch, and
some can use an optional wire-drive to perform MIG welding.

Rewiring for an
arc welder
Except for a few small, household-current machines
capable of 100 amps or less, even the most basic AC arc
welders require 220V input. Depending on the present
wiring of your house, this may require an additional expense in rewiring to accommodate the welder, a factor to
take into consideration when choosing the right system for
you. Some homes already have a 220V outlet for hooking
up an electric clothes dryer or stove (the most common
household appliances to run on this voltage), but this outlet
may not be where you need to weld. If your washer/dryer
setup is in the garage, you're ahead of the game, and
rewiring may not be necessary. Likewise, if you plan to do
most of your welding in the kitchen, then your case is sim4.9 Contractors often use an engine-driven arc welder
plified.
mounted on a truck bed or a small trailer. Besides powering
If you have to run a new circuit in your house to put
the welder, the gas engine also has a large generator to run
220V where you need it for the arc welder, put it on it's own
power tools in a remote work site.
separate circuit with a 30-amp circuit-breaker. The kind of
current you may be drawing when welding thick material
may blow a standard 15 or 20-amp household breaker. Call a few electricians
before you buy an arc welder. Tell them what size electrical box you have (how
many amps), how many open spaces there are for new circuits, and how far a
new 220V circuit would have to be run to get an outlet in your proposed welding
area. They should be able to give you a rough estimate of the rewiring costs. It
may cost as much or more than the welder itself, and may ultimately influence
4-5

Haynes Welding Manual
what kind of welding machine you finally purchase.
Even if you do have an existing 220V outlet you can
use, you'll be rudely surprised when you find the welder
can't be plugged in, at least not directly. The arrangement
of prongs on the welder's power cable is slightly different
than the layout of the typical 220V home appliance plug.
You can make or purchase an adapter, or have the electrician install an outlet box in your welding area that matches
the kind of plug on your arc welder (see illustration). Before plugging a new stick welder into a household 220V
outlet with an adapter, you should have the system
checked to be sure the wire gauge and circuit-breaker are
up to the task of handling a welding machine.

4.10 Even if you do have a 220V circuit in your shop for a
clothes dryer, you'll find the outlet prongs are different on a
220V welder's plug. You either have to rewire your outlet box
to accept a welding plug, put a household 220V plug on the
welder's power cable, or use an adapter.

The arc process

All electrical-welding processes use the flow of electricity to create heat. The power flows from the torch or
electrode to the work, which is grounded to the source at
the machine. In arc welding, the consumable electrode or
rod makes the connection that creates the arc to the piece
being welded. The welding rod is a metal rod coated with a hard flux material. As
the arc is created when the tip of the metal comes to the workpiece, the heat
generated at the bead is 6000° F or more, which melts both the parent metal and
the filler rod, while simultaneously vaporizing the flux coating to create a gas
shield around the bead, protecting the solidifying weld from contamination by
gasses in the air (see illustrations). The flux actually re-solidifies on top of the
bead as a hard coating of flux and slag, and when you look at a completed bead,
you'll see a dome of ceramic-like material over the weld. At this point, the weld
doesn't look very impressive, but when you remove the slag with a chipping
hammer, a beautiful, clean bead is revealed (see illustrations). Depending on
the type of rod and amperage used, there may also be some spatter (tiny beads
of metal) stuck alongside the bead. Most of these beads will come off with stiff
application of a wire brush, and more stubborn ones can be removed with the

4.11 Arc-welding electrodes or rods are a metal wire,
covered with a flux coating. The metal wire must make initial
contact with the work to initiate the arc, then it is pulled back
to a proper rod-to-work distance, the vaporizing flux makes a
shielding gas, but also deposits a layer of slag over the weld
as it forms, to further protect the weld from contamination.
4-6

4.12 This is what you will see through your helmet and
welding lens. The arc is intensely bright, but the lens cuts this
down to just a bright glow around the arc itself, here you can
just about see where the shielding gas cloud forms
around the arc.

Arc welding

4.13 The slag formed over the weld bead must be removed
with a chipping hammer like this, and most spatter and slag
residue can be cleaned up with a wire brush after chipping.

4.14 At right on this bead, you can see the dark gray slag
coating covering the weld. The portion at the left has been
chipped off to reveal a bright, shiny weld.

chipping hammer or a chisel.
Making your first passes with the AC stick welder will be relatively easy, although really good passes will require considerable practice. The instruction
book that comes with your welder will specify the right rods to use for various
materials, and the amperage to set for different thicknesses of ferrous metal. The
rest of the technique is finding the most comfortable position for your electrodeholder hand, and maintaining the proper arc distance and travel speed to make
good joints.

Safety considerations
With every method of welding, safety is of paramount consideration, but
each type has precautions that apply to that type of equipment in particular. In all
forms of electric welding, including arc welding, high-amperage electrical current
is the primary hazard. All of your cables, plugs and leads should be inspected
regularly for any signs of defects. Even dirt or paint overspray on connections
can cause arcing and poor welds. Water, of course, is a good conductor of electricity, and therefore should be avoided in the work area. Your clothing, equipment and especially the floor must be kept dry to avoid the possibility of electrical shock. Rubber-soled shoes are recommended, but athletic shoes
(non-leather) are not. Most experts will tell you not to wear metal jewelry such as
watchbands, rings, bracelets, necklaces or belt buckles when welding. If electricwelder power comes into contact with metal articles you are wearing, they can
become instantly hot to the point of melting, or can cause electric shock.
Of the electric welding methods, arc welding requires the most protection of
your face and body during welding. The intensity of the arc produces strong UV
and infrared radiation. Any skin exposed during the welding process can become
burned, in severity ranging from mild sunburn to serious burns, with the symptoms not appearing until eight hours after the exposure. Leave the top button unbuttoned on your shift and you'll have a nasty V-shaped burn on your neck after
only a short while arc-welding. Likewise, wear fire-resistant, long-sleeved shirts,
and keep your sleeves rolled down at all times. Keep these shirts just for welding,
and tear off the pockets if they have any, or keep them empty and buttoned. An
experienced weldor friend of ours was recently burned painfully when welding
overhead with just a shop shirt on — a hot bead of spatter went right into his shirt
pocket and burned into his chest. Without the pockets, there's a chance the
bead will roll off onto the floor rather than stay in one spot on your shirt. For this
4-7

Haynes Welding Manual
same reason, your pants should be kept uncuffed, and never tucked into
your boots.
If you are going to be doing arc-welding often, we'd recommend you
invest in some leather safety clothing, like jackets, vests or pull-on sleeves
that go over your regular shirt. Arc-welding is prone to more spattering
than other types of welding, and these leather weldor's clothes are highly
resistant to arc spatter.
Probably your most sensitive and fragile body parts exposed to welding dangers are your eyes. Even the tiniest bit of spatter in an unprotected
eye can have truly long-lasting negative effects. Always wear a full-coverage safety helmet when welding, preferably with a leather flap at the bottom-front that protects your neck area. Especially when welding overhead, like underneath a vehicle, wear a cloth cap backwards ( bill to back)
to cover your hair and the back of your neck. Your helmet should be
equipped with the proper safety lens for the type of welding you are doing,
or your eyes could receive overexposure of UV and infrared rays in a very
short time. Never observe anyone else doing arc-welding unless you are
wearing proper eye protection, and make sure that when you are welding
that there is no one observing you who could be hurt by watching, particularly children. Watching too much arc will not show immediate effects,
but later the affected eyes will be sore, and with a sensation almost like
having lots of sand in your eyes. If you do not yet have your own welder,
but want to watch someone else work, get your own helmet to observe
through. If you do have a welder, you may want to keep a spare helmet
4.15 The arc spatter and radiation are
around in case someone wants to observe your welding prowess.
dangerous. Do not allow any bystanders to
Your eyes can be permanently damaged by overexposure to arc rays,
observe the arc while you are welding. Also,
but
they
must also be protected when working around most shop equipnotice how much smoke is around the
ment,
such
as grinders, mills, drills and sanders, all equipment that may be
weldor's helmet here. The fumes are
involved in your welding project. Keep several pair of good safety glasses
dangerous and you should have an electric fan
around your shop, the kind that have protection all the way around the
of some kind to blow it away from you when
you are welding in a corner like this.
sides. After arc-welding, you will also want to wear these safety glasses
when chipping slag from your welds. The little fragments that break off are
like glass. Always keep a very complete first-aid kit accessible in your work area
in case of accidents.
A particular hazard with arc welding is the presence of fumes. When the
electrode is consumed, the flux is vaporized, creating the shielding gasses that
protect the weld from contamination during formation. Depending on the metal
being welded, other gasses may be released as the metal is melted. Most welding gasses are colorless, odorless, tasteless and inert, but this is not to imply that
they are harmless. Any of the common welding gasses can displace oxygen, and
when you are breathing in air that contains less than 18% oxygen, you may experience dizziness, or even lose consciousness. For this reason, arc welding, or
any welding process, should be performed only where there is adequate ventilation. In the case of arc welding, there is less chance of the shielding gasses being
blown away and causing a bad weld, so if you find yourself welding in one spot
too long, or in a confined area, you can use a household fan somewhere in your
work area to maintain air circulation.

Beginning arc welding
If you have already read the previous chapter on gas welding, what you will
have learned in practicing that mode will help you greatly in learning all other
forms of welding, including arc. Stick (arc) welding is easier in some ways than
gas-torch welding, and more difficult in others. Practice and more practice will
put you on the road to good welding in any mode.
What you will find different at first about arc welding is that you only need
one hand. The electrode holder and its electrode or rod is it, other than the
4-8

Arc welding
ground clamp, which should be clamped to your workpiece or your steel welding
table. The rod is both the source of filler metal and the shielding gasses, which
are generated when the flux covering is vaporized. Have some scrap steel handy
and some 1/8-inch rods. There are a great many specialized rods, but one of the
most common is an E-6011, which is one of the easier rods to start and maintain
an arc with. Although the arc process only involves the one hand-held tool, you
may find that the 14-inch-long rods put your hand a much further distance from
the weld area than the other welding processes. One end of the rod is bare of any
flux coating for about an inch, this is the end you put in the electrode holder.
It's a good idea to practice the arc "setup" without turning on the welding
machine. Just situate yourself comfortably in relation to the work, and practice
holding the electrode 1/4-inch away from your work joint or seam area, following
the proposed seam while slightly weaving the electrode tip side to side as you
travel along. This will give a feel for what is required in terms of coordination.
Now if you're ready, set the machine for the right amperage for the thickness
of your scrap steel, say 1/4-inch steel plates, or perhaps slightly hotter than the
instructions recommend to make it easier to learn the starting procedure. One
drawback of the arc-welding process is getting the arc started. You can't just flip
down your helmet or lens and stab the rod against the work.
The starting procedure has been described as similar to striking a match, in
which you draw the rod tip across the area you plan to start the bead. At some
point in your "scratch" the rod will momentarily contact the work and the arc will
start, but the rod must continue moving. Arc welding is essentially a process of
creating a short-circuit across the rod and the work, and it can only be started by
a momentary contact of the two. Once started, this short-circuit heats the air
around the weld and ionizes it to the point where the air conducts electricity and
continues the arc without actual metal-to-metal contact. As soon as the arc
starts, the rod tip must be pulled back to the suggested tip-to-work distance. All
of this sounds tedious and difficult, but you will pick the technique up in the first
half-hour of practice.
If you touch the rod to the surface for more than a split second, it may stick
firmly, in which case the rod can get red-hot for its whole length in a very short
span of time. As soon as you feel the rod stick to the surface, squeeze the clamp
on your electrode holder to release the rod, which is the only way to stop the rod
from melting. The hot rod will stay stuck to your work. You can take it off with
some pliers, but when it is really hot, don't try snapping it off with your gloves, it
may burn right through the leather. Let that rod cool off and start another rod until your have mastered the arc-starting process. When you are more experienced,
you'll react quickly enough to a stuck rod that you can simply break the connection immediately by twisting the electrode holder and rod side to side.
Another method of arc starting favored by some weldors is a "tapping" style,
in which you quickly tap the electrode tip to the work to start the arc, not in a
"pressing" action, but in a short in-and-out jerk that makes contact at the bottom
of the tip's travel toward the work.
Once you understand the starting process, the tip to work distance is next.
When the arc starts, you must pull the rod back for a second to make a relativelylong arc (about twice the thickness of the electrode you are using) as a way of inducing some preheat into the metal, then immediately drop the rod closer, to
about one rod-thickness away from the work. Keep the rod moving along the
seam, and move the rod side-to-side slightly as you travel. Some weldors use a
movement like a series of tiny, overlapping ovals, others a zigzag or even a
"weaving" pattern. Stay in one place too long or with the rod tip too close to the
work, and you'll melt a hole in your work; also, if you pull the rod back too far,
you can lose the arc process and have to restart. On small seams in thin materials, you won't need to weave the rod much. When joining thick materials, the
joint is usually Vee'd or beveled, and a straight pass is made along the bottom of
the joint, followed by one or more passes where the oscillation or weaving of the
tip spreads the bead circles out larger in the wider gap at the top of the bevel.
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Haynes Welding Manual
The rod should be more or less vertical when the arc is
struck initially, where it can really preheat the metal, but
should be angled forward (in the direction of travel) 20-30
degrees as you make your pass, i.e. you hold the electrode
holder somewhat ahead of the puddle, with the rod 20-30
degrees from vertical (see illustration). Try making some
straight passes along a flat, horizontal plate, until you get
the hang of running a bead. Run a straight bead with the
puddles being about twice the diameter of the rod you are
using. While you are welding, it is important to remember
not to watch the arc, but rather focus on the puddle you are
leaving behind it. The shape, size and crown of the puddle
are the keys to determine how you are doing.
When you have the travel speed, amperage and rod-towork distance correct, you'll find out why they used to call
an AC arc welder a "buzz box," because you'll get a very
satisfying sound, which is a steady, crisp noise something
4.16 The electrode is usually held more or less perpendicular
like bacon frying. This sound your welder makes, and the
to the welding surface to start the arc, then laid back to
way the bead looks will tell you much about your progress.
continue the bead. Some weldors prefer a forehand
technique, others a backhand direction, such as here.
If you have the arc gap too large, you'll have uneven puddling, a bead that is too wide, and the sound will be uneven.
Such a weld will have more than normal spatter. On the other hand, if you have
the rod tip too close, it may stick to the work, the bead will be high but not very
wide and the sound will be softer.
One of the hard parts to learn here compared to gas welding is that the part
you are holding, the electrode holder, must continually be brought closer to the
work as the rod gets shorter, while in gas welding the torch stays the same distance from the welding. The hand-eye coordination you must learn involves
keeping the tip the right distance from the work, the rod at the right angle, the
correct speed of travel, and compensating for the shortening of the rod. Speaking of electrode length, when the rod gets fairly short, it's best to stop and then
re-start with a new rod. When the electrodes are too short, a lot of extra heat
travels to the electrode holder and your gloved hand.
The speed you travel is almost as important as the rod-to-work distance. If
you travel too fast, the resulting bead will be too narrow, and you may not get
100% penetration. If you proceed too slowly, you'll wind up with a large bead,

4.17 Arc-welding electrode holders are usually a clamp-like
affair, with notches to allow the rod to be clamped at several
different angles. Many arc weldors prefer this style, called a
short-stub, in which the rod is inserted and the handle is
twisted to lock the rod in place.

4-10

4.18 To achieve a different rod angle with a short-stub
electrode-holder, just bend the rod near the holder to the
desired angle. In some situation, where you have to reach
down inside something to weld, the rod can be bent
straight out.

Arc welding
and you may induce excessive heat into the
workpiece. After you have practiced speed
and arc-to-work distance, practice stopping
and starting a bead. In real-world welding,
you will encounter seams that take several
sticks to complete, but you want the completed weld to look continuous even if it
wasn't. To stop a bead, when you have to
change electrodes for instance, just pull the
4.19 Too much amperage and the bead will sink too far into the work and
rod back up quickly to break the arc. Any
leave cratering or undercutting on the top. If your welding speed is too slow,
time you stop arc welding, you must chip
the bead can build up unnecessarily on top.
the slag away from the place you last
stopped, before continuing with a new rod. When you pick-up
again with the new rod, start about 1/2-inch ahead of where
the last puddle was and re-strike your arc and proceed. The
arc will melt the original "last puddle" and continue the bead
without any apparent interruption. This will take some practice.
If you have seen professionally-welded seams, they look like
they were applied by a continuously-operating machine, so integrated are the stops and starts, and that's what you are
shooting for.

Types of joints
After you are experienced at making straight beads on
plates lying flat in front of you, begin to practice on joints between two pieces. The simplest to learn on are butt joints. If
the material is 1/4-inch or thicker, you should bevel the edges
4.20 In these three practice arc-welding beads, the leftof both parts before welding. As with any parts to be welded,
hand bead was too "cold", meaning not enough
either ferrous or nonferrous, cleanliness of the work is very imamperage. The center weld is OK, and the right has too
portant to making a sound weld, so grind the pieces to be
much amperage, with increased spatter and too wide a
joined not just on the bevel, but at least 1/2-inch on either side
bead for the thickness of the material.
of the joint, so that impurities don't contaminate the weld.
Most seams are started by tacking the parts together at either end and
perhaps several places along the way, depending on how long the seam is.
Because of the growth of the parts from the heat of welding, you may need
to "build-in" a gap between them during the tacking phase. Some weldors
place a small piece of bare copper wire between the two parts, tack one
end, and then move the wire "spacer" to where the next tack will be, continuing so that the two parts are tacked slightly apart from each other with an
even gap. As you weld up the seam, the parts will "grow" together. Whenever we mention tack-welding in conjunction with arc welding, remember
that the slag must be chipped and wire-brushed away from the tacks before
you "connect the dots" with continuous welds.
Depending on the thickness of the material you are working on, you may
make a two-pass weld, one on the top and one on the bottom. This would
only be feasible on plates, not on pipe or tubing, but makes for a very strong
joint, and the opposing forces of distortion may keep the parts flatter than if
you made only one large pass on one side. Looking at an end view of the
plates, the first pass should go into the joint a little more than halfway, then
the second weld on the other side should bite into that first bead for a completely-welded joint. Usually, such joints do not require as high an amperage
4.21 Welding large plates, such as here
setting on the welder as for making a single-pass weld.
where new metal is being added to a John
One of the common uses of arc-welding equipment is in farming and
Deere dirt scoop, requires either multi-pass
ranching, where the equipment being repaired is usually too large to bring
welding, or using a large rod at high
into the shop. That means that most welding that requires a bottle of shieldamperages. This seam was done with a
ing gas may be too susceptible to wind to be effective, and the arc-welding
single pass with 1/4-inch electrodes.
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Haynes Welding Manual

4.22 Here half-inch plate on the sides was welded with one
pass, but a gap was left where the one-inch, beveled lower
plates join. The bigger plate will be welded with several
passes and strength is improved if the joint starts all
the way at the ends.

4.23 An outside corner weld on 5/16-inch plates is made with
one pass with a wide weaving pattern, spread equal
heat on both parts.

process is advantageous here. Also, most farm equipment is rather heavy, with
large components, and arc welding's ability to fill large breaks, weld castings,
and deposit large quantities of filler metal if needed makes arc a good choice.
The visual beauty of the welds is seldom a factor in agricultural repairs: it's getting the equipment back into service that counts. Building up of worn agricultural
parts is a common task in which the weldor makes repeated beads right next to
each other to literally build a new and higher surface on the part. The work is tedious, but necessary.
Generally, you make the first pass in normal welding mode, then make succeeding passes with the electrode held at a slight side angle to the work. Remember than when arc welding, the hot filler metal is virtually sprayed off the end
of the rod like a spray gun, and where you aim the rod is where the metal will be
deposited. The slight side angle allows the succeeding passes to bite slightly into
the previous bead. Alternate the direction of the beads and overlap them about
one-third of the bead width. There are even special rods made that deposit a
hard-facing on metal. These can be used to renew or create a hard cutting edge
on a part, which can be later ground or filed to an edge that will stay sharper
longer than the parent metal. When making any kind of 'buildup" welds, each
bead must be chipped clean before you begin the next pass, or slag and impurities could be trapped by the next bead. Also, when you are building up a part,
rather than fusing a seam as in regular welding, you can run the bead much wider
than we have suggested so far. The idea here is not to fuse two parts but to deposit as much metal as possible onto the surface. In these cases, you can
"weave" the rod tip back and forth in a zigzag or other pattern to make a wider
bead.
You will find that "out-of-position" welds, welds that are not made with the
parts lying flat in front of you on the welding table, are the toughest to learn. Corner joints, vertical seams and overhead seams offer increasing levels of challenge. Corner joints are commonly found when joining two plates where one
plate is perpendicular to the other, like a T. The electrode should be at a 45° angle between the two parts, so that equal heat and filler metal is directed onto
both pieces. In some cases, you may find you have to place the arc such that it
puts more heat on the bottom plate (which is dissipating more heat from the joint)
while aiming the electrode "spray" more at the upper plate to avoid "undercutting", which is when you see a slight crevice along one or both edges of a welded
joint after you chip the slag away.

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Arc welding

4.24 This sample weld shows how large plates are joined by multiple passes with large rods. Compare this front view (right)
where the weld passes began, to the cutaway photo (left) which illustrates how integrated and free of contaminants even such a
large weld can be.

If you are joining heavy plates, the fillet weld may take three passes, in which
case the first bead is put right into the corner, then a second pass is made alongside that one with the electrode aimed to "spray" slightly more toward the side
between this bead and the corner's edge, and the third pass is aimed to the opposite side of the center (see illustrations). If, on the other hand, you are welding a thick plate to a thinner one, then favor the angle of the electrode towards
the heavier plate to give it more heat. In practicing such welds, it may be advantageous to use plates that are only an inch or two by six inches. This will make for
less work when cutting a cross-section through them afterwards to examine your
weld for penetration and lack of voids or impurities, especially if you have to
hand-hacksaw through them.
While basic, flat butt joints are most common in typical home/shop projects,
the Tee or fillet joint and the lap joint make up the majority of welds in industry
and construction. The lap joint, where one plate lays on top of another, is approached much like the Tee joint, with the electrode angle at about 45°, aimed at
the inside corner where the two plates meet. If they are different thicknesses,
then the electrode may need to be aimed to give more heat to the heavier piece.
Another difference between industry and home projects is that you will seldom
encounter any joint that requires more than one pass to complete in a
home/shop project. The use of really thick plates just isn't that common in automotive, arts and crafts or making shop equipment, with the possible exception of
building an engine stand, which might have a half-inch plate welded to a tube for
the part the engine-holding arms attach to. This is one reason that arc-welding
isn't that common anymore as a home/shop tool. Other methods seem better
suited to the thinner materials encountered in hobby projects, though farm
equipment repair does sometimes require the large-scale abilities of an arc
welder.

Choosing electrodes
Your home AC arc-welder will probably come with an assortment of basic
welding rods to practice with. After that you'll have to shop at your local welding
supply or order from a catalog, and you should have a good idea by then of what
type and thicknesses of metals you'll be working on, and thus what size and type
of rods to use. Your local supplier should be able to give you good advice on
what best suits your purposes. As you read or talk with other people about arcwelding, you may hear the rods termed any of the following: stinger, rod, elec-

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Haynes Welding Manual
trode or stick. They all mean the same thing.
While there is a confusing array of arc-welding electrodes on the market, the bulk of them are specifically designed for industrial and other specialty usage, and you will
never have a call for them. There are perhaps only a half
dozen rods that would cover your needs. Rods differ in the
type and diameter the central metal wire is made of, and in
the thickness and composition of the coating of flux as well.
In actual use, the flux burns away at a slower rate than the
rod inside, which makes for a sort of "collar" around the tip
of the rod, further shielding the weld process and helping
concentrate and direct the "spray" of metal coming off the
wire (see illustration).
Many of the hundreds of special-purpose arc rods are
designed strictly for the professional DC welder, so you
won't have to worry about those if you're using a typical
220V home AC welder. For your needs, there are perhaps
4.25 Some arc rods melt the wire at a faster rate than the
three types you will use the most. Of these, E-6011 is the
flux, leaving the wire recessed inside. During the welding, this
designation for what is the most commonly-used electrode.
makes a more concentrated arc spray. When re-striking an
arc with such a rod, the extra flux around the tip must be
It is one of the easiest for a beginner to master, can be used
broken off with your gloved fingers or pliers (with the rod
on AC or DC, in virtually all positions of welding, and can be
cooled off) to expose the metal for re-striking the arc.
used in situations where the parent metal hasn't been prepared spotlessly. It's main drawback is that it produces a
lot of spatter. Where the appearance of the weld is less important than the ability to make a strong joint on rough or
dirty materials, such as in farm equipment repairs, this is a
good choice. After practicing with this one, you may want
to move on to more "sophisticated" electrodes. The E-6013
rod works great in many situations, and, although it requires
better surface preparation and cleaning than the 6011 rod,
it will produce much better looking welds, is suitable for a
variety of positions and handles metals up to 3/16-inch
thickness with most home-type buzz-boxes. It can be used
for lots of projects like building shop equipment, and there
are even variations on this rod from different manufacturers
that are specifically for sheet-metal work, in sizes down to
1/16-inch. When the size of a welding rod is mentioned, it
refers only to the diameter of the wire inside. Obviously, the
flux coating makes the rod appear much thicker, and if you
need to check a rod, measure the bare end meant to go
4.26 You'll find a wide variety of electrodes at your welding
into the electrode holder.
supply store, but there are only a few rods you will use in
There has been a variety of methods used in the past to
normal home/shop projects on mild steel. Don't buy much
identify
welding rods, including numbers and color codes,
more than you will need for the next project.
but most rods you find today have both a number and code
from the manufacturer, as well as a standard A.W.S. number, such as E-6013 (see illustration). These standard designations come from
the American Welding Society and should be easy to find somewhere on the
boxes of rod you buy. The E stands for electrode (for arc welding), the 60 part is
multiplied by 1000 to give you the tensile strength of the wire (in this case, 60,000
psi), the next digit is a code for the type of position the rod is recommended for,
and the last digit refers to the type and polarity of the current required. The 1 in
our example in the "position" spot indicates the rod is good in all positions, a 2
would mean flat position. The last number indicates that this rod can be used
with AC or DC, and on DC can be used with straight or reverse polarity, though
straight polarity is seldom used.
Another good rod for starting out is E-7014, which is higher in strength and
produces good-looking beads. It and the E-6013 mentioned earlier require a little
different arc procedure than what we have described so far. These are called

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Arc welding
"contact rods" because, instead of maintaining a basic
1/8-inch gap as you go along, you keep the tip just in
contact with the parent metal, in a sense dragging the
rod lightly along the seam.
A special-purpose rod used in repairing cast-iron,
such as automotive blocks, cracked heads, transmission
cases, and various farm equipment, is EST, although
there are several brand names in the trade just for castiron rod. Most rods for this purpose have a high nickel
content. Although these rods are available, it doesn't
mean that cast-iron welding is easy. Any cast part should
be thoroughly preheated to 400° F or better to prevent
cracking after the localized heat of welding is induced
into the part. Parts, depending on their size, can be
heated in an oven or with a rosebud tip on an oxy-acetylene torch, using temperature indicating paints to tell
when you have it evenly heated to the proper tempera4.27 This is the bare end of the rod, where it fits into the
ture. Even then, there can be cracking problems. It can be
electrode holder. You can judge the size of a rod from this
bare end - don't measure the flux coating. Rods are marked
very difficult to get a cracked cast-iron part thoroughly
as to their type and color-coded.
cleaned before welding, usually requiring a deep Vee to
make a good repair. Better success on cast iron may be
had by welding in short strips 1/2 to 3/4-inch long, with
the part cleaned and allowed to cool off in between. In
automotive use, broken cast-iron exhaust manifolds are a
common repair item, and the high-nickel rods can be
used successfully, but a well-used exhaust manifold
needs to be sandblasted inside and out beforehand to
get rid of as much of the carbon baked into the pores of
the casting as possible. Usually, a brand-new casting will
take a much-longer-lasting weld, such as when modifying
manifolds to accept turbocharger flanges. Most small
cast-iron repairs are better made with brazing by an oxyacetylene torch, where much less heat is introduced, although the part should still be preheated.
Arc-welding electrodes are also marked with color
codes. Usually, the flux coating itself is a different color to
indicate a type, as well as markings or dabs of colors near
4.28 Rods must be kept dry for the flux coatings to work
the tip. The E-6011 has a white flux coating and a blue
properly. Keep only as much rod as you need, and store
spot color, E-6013 is a dark tan with a brown spot, etc.
them in a tight container such as this Lincoln plastic rod
Proper storage of electrodes is critical to their perforbox with gasketed screw cap.
mance (see illustration). They are very susceptible to
moisture, and must be stored in a perfectly dry environment. Once they absorb moisture, the flux coating tends to loosen and flake off,
and the rod is useless. In large production operations where critical welding is
done, the rods are stored in a special oven that keeps them at a constant 100° F
or more to ensure that they are dry, and only enough rod that will be used in a
few hours is removed at one time from the oven.
In a home/shop situation, buy only as much rod as you think you need to
keep around for unexpected projects, a few pounds of each type you normally
use. Keep these in either sealable metal cans or plastic bags with desiccant inside. Desiccant is a moisture-absorbing compound, the stuff we always find
packed in little "teabags" with electronic components and camera equipment.
You can save up these bags whenever you get a new electronic goodie. The
bags can be dried out in the oven for a short while, then put into the container
holding your welding rods. If you have a bigger project in mind, buy what you
need for that project only, fresh from the welding supply, and don't keep any
large quantities around. We have seen a variety of methods used by weldors to
keep electrodes dry, including racks of custom-built metal tubes with screwcaps.

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Haynes Welding Manual

4.29 These L-TEC portable arc power sources are
lightweight, and offer up to 90 amps on the STW 90i (right)
and 130 amps on the STW 140i. Unlike most small arc
welders, these are DC, and can even be set up with a
torch and power adapter to run a TIG torch. They
are available for 110V or 220V input.

4.30 The Eastwood Company markets a lot of equipment and
supplies for auto restoration, and this is their small 110V arc
welder. At its maximum of 70 amps, it delivers a 10%
duty-cycle, so you won't be welding any bridges together,
but it only weighs 26 pounds, so it's extremely portable
and welds up to 3/16-inch.

If you have reviewed the above introduction to arc-welding, you should have a
good idea by now of whether it will suit your particular welding needs. It can be
both easy-to-learn and challenging, simple and complicated, and can produce results from "farm-grade" (where strength is primary) to automotive-quality to
atomic-reactor quality. It has the advantage of simple operation, low maintenance,
low initial cost (not considering the cost of rewiring for 220V if necessary), and the
unmatched ability to weld outdoors without being affected by wind, making it suitable for structural-steel construction, pipelines, iron-fence work, and farm repairs,
as well as being the best choice for welding and repairing thick materials.

4.31 Auto manufacturers build cars with spot-welding
machines, and with Eastwood Company's spot-welder gun,
you can repair one the same way. The replaceable
electrodes last for 60-100 welds.
4.32 The spot welder is a self-contained mini-arc-welder,
designed for joining sheet-metal panels on auto body work.

4-16

MIG welding
Welding books written as recently as ten years ago may have recommended
oxy-acetylene and arc-welding equipment as the basic tools for home/shop
welding. At that time, MIG, or wire-feed, welding equipment was considered too
expensive for amateur use, despite its advantages. The MIG equipment was recommended, and indeed was originally designed, for high-production shop work
only. Much has changed in the intervening years, and the introduction of lowercost MIG units and the competitiveness of the marketplace has brought wirefeed welding into an affordable range for the home/shop weldor.
An outgrowth of arc welding, the MIG process was conceived as a way to
speed up production in industrial applications. The basic difference with MIG,
which stands for Metal Inert Gas welding (sometimes also referred to by its technical description as Gas Metal Arc Welding,
or GMAW), is that the welding filler rod is
automatically fed through the gun whenever
welding takes place. The weldor doesn't
need to stop to change arc electrodes. The
Airco company developed the MIG process

5.1 The use of wire-feed MIG welding has expanded greatly in the last ten
years to encompass body shops, muffler shops, race-car builders and home
hobbyists as well as the industrial production work it was designed for. It has
advantages of speed, simplicity, cleanliness, and the ability to work well on
thick and thin materials.
5.2 Among the compact MIG welders in the 110V field is the L-TEC MIG 130,
which features 100% duty-cycle at its 30 amp setting for thin material, and has
a 25% duty-cycle at 130 amps. It's designed for body shops, hobbyists and
light maintenance use.

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Haynes Welding Manual

5.4 The Miller Electric Co. makes a variety of larger professional welding
machines, but they also offer this Millermatic 130, which has a 20% duty
cycle at its maximum 130 amps, putting it right in the midst of the 110V
home/shop MIGs.

5.3 For the larger-scale shop, the
heavy-duty 220V machines like this
Migmaster 250 offer more amperage,
more amp settings, higher duty
cycles, and various extra features for
timing various weld functions.

5-2

right after W.W.II, and it has been refined continuously ever since.
The many advantages of the MIG process, besides the basic one
of not having to stop to change electrodes, include: being able to weld
in all positions; there is no slag removal and the welds are much
cleaner and with very little spatter compared to arc welding; the welding can proceed a lot faster than with other methods because the wirefeed rate is automatic and adjustable, which also makes for less distortion of the workpiece because less heat is concentrated on the seam; the
process works well on joints that are irregular or have gaps; and the amperage,
wire size and wire-feed speed can be tuned down to do ideal, almost distortionless welds on thin sheet metal. There are more advantages that relate to how the
weldor uses the equipment, and we'll see these points as we continue.
There are technically three different processes of metal transfer with MIG
welding equipment, but the one we are concerned with is called the short-arc or
short-circuit process. The other types are used in larger industrial welding
processes where high amperages and large-diameter welding wire is used. Most
of the MIG machines suitable for home/shop use are designed for short-arc
process, where the molten end of the welding wire touches the weld puddle and
creates a short-circuit, and the wire diameters are from .023-inch to .045-inch.
Amperages in these machines are seldom higher than 225 amps yet can handle
materials from the thinnest auto-body sheet metal to plates as thick as 1/2-inch,
a range that certainly covers everything the home/shop weldor, metal sculptor,
body man, farmer or ornamental iron worker will have a call for.
In the short-arc process, the basic components of the MIG equipment consist of the welding machine, which contains an AC-to-DC rectifier with constant
voltage potential and a wire-feeding mechanism that holds a large roll of wire, a
bottle of shielding gas (in most models), a welding cable that routes wire, power
and gas to the torch, a simple trigger-operated torch or gun and a ground or
work cable. In operation, the weldor brings the torch down to the work until the
bare wire electrode, which sticks out of the gun 1/2 to 3/4-inch, is touching the

MIG welding

5.6 There are very few user controls on the panel of a basic
MIG welder, just a switch for the different amperage settings,
and a variable knob for controlling the wire-feed speed.

work where the
seam is to be; he
then flips his helmet or lens
down and pulls
the trigger. The
trigger immediately puts power
to the wire, which arcs against the work to create very localized heat while
shielding gas is simultaneously released that puts a shielding "envelope" over the
forming weld, preventing contamination (see illustration). The short-arc process
actually is alternately melting and not melting the electrode wire about 90 times a
second. Each time the wire touches the work it melts and creates a gap between
itself and the work, which is when a drop of molten wire attaches to the work and
blends in. The constant arc-on-arc-off is what gives the MIG process its characteristic "sizzling" sound when you weld with the correct wire speed, amperage
and travel speed. The current used is DC with reverse polarity (like most of the
professional arc-welding machines), which provides for deep penetration. Only a
few applications and machines have the straight polarity option, and this is only
for shallow-penetration work where the coverage or speed of deposition is most
important.
The weldor has few controls to worry about in setting up a MIG machine.
There is a voltage knob or switch to control the current, and a wire-speed knob
that determines how fast the welding wire comes out of the gun (see illustration). Selecting the amperage is based mostly on the thickness of the material to
be welded. A rule of thumb from the Miller Electric Company is "one ampere for
every .001-inch of plate thickness." For example, an 1/8-inch (.125-inch) plate
would require 125 amps. Of course, this doesn't mean that a 1/2-inch plate
would take 500 amps, because large plates are generally beveled before welding
and joined with a root pass in the bottom and several more passes on top. There
are, however, industrial machines that routinely weld large plates, such as on
ship decks, with very large wire diameter and high amperages. This is just a general rule, and other factors, such as the wire speed and welding travel speed affect the current requirement. In the smaller home-type MIG machines, the amperage settings are fixed, with perhaps four different positions on the current
knob, but the wire-speed knob is infinitely variable on all MIG machines. The
>—Molten weld
metal
5.5 The cable leading to the MIG torch has to carry several
different materials, from the electrical current, to the wire
electrode and the shielding gas. The torch itself is rather
simple, feeding the wire out to maintain a short-circuit arc
against the work, while keeping the weld under an envelope
of shielding gas.

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Haynes Welding Manual

5.7 The basic MIG torch is quite simple. Inside is a guide tube that the
wire comes through, a switch that turns on the power and the shieldinggas flow. The curved neck, called a "swan neck", holds the contact tube
and the nozzle.

5.9 Most MIG nozzles just twist off past a snap ring, exposing the
contact tube (arrow). You should keep an extra nozzle as a spare,
and several spares of the sizes of contact tubes (below) that you
use most. Eventually, you will weld the wire to the contact tube, and
have to unscrew it to get it off, then clip off the wire and install a
new tube, also called a contact tip.

5.8 The wire must fit the contact tube closely, as
this is where power is transmitted to the electrode
wire. Note that the contact tube is recessed inside
the nozzle, and the wire sticks out 1/2-3/4-inch
from the nozzle.

5.10 It's important to keep a pair of side-cutter pliers
handy at all times to your MIG welder. Not only do you
need it to maintain the correct protrusion of the wire
from the nozzle, but when the wire develops a ball on
the end, the arc is easier to start if you snip the ball off.

more expensive, more professional MIG machines have variable-current output,
or at least more positions on the switch, and may have other optional controls for
timing weld events.
The torch cooling on almost all MIG machines, certainly the ones we are
considering for home/shop use, is by air, although there are some industrial applications which have a water-cooled torch because of the heavy wire and high
amperage being used. Looking inside the MIG torch, the main body of the handle
contains the switch or trigger, a wire conduit with a metal or plastic-tubing liner,
and the curved "swan neck" that comes out holding both a contact or wire guide
tube and a nozzle. The contact tube is so called because it actually puts the
power to the wire. Usually made of copper, the contact tube also keeps the wire
output centered in the gas cup or nozzle (see illustration). Since this is where
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MIG welding

5.11 For some MIGs, there is a variety of different-size nozzles, some
with special purposes like spot-welding. At the center here is a tool for
scraping debris from inside a nozzle.

the power is transferred to the wire, the contact tube must have a specific size
related to the size of the electrode wire being used. Because of the unavoidable
wear in the contact tube, and occasional arcing that ruins a contact tube, these
are considered consumables in MIG welding, and you should have several
spares of any of the sizes you normally use.
The nozzle's main function is to contain the shielding gas in an envelope
around the arcing wire. Most MIG machines have only one size nozzle, but in
production applications smaller nozzles are used on smaller-amperage work and
larger nozzles on bigger jobs (see illustration). The nozzle takes some punishment in MIG welding, with spatter and weld debris constantly building up inside.
Special tools are available that scrape out the buildup, and most MIG weldors
use an anti-spatter or "nozzle-shield" gel or spray to keep down the buildup and
allow easy removal of the gook when necessary (see illustration). Obviously, if
too much debris builds up inside the nozzle, it will affect the gas flow to the weld
area and thus cause deterioration and unevenness in the bead. The sprays can
be directed inside the nozzle after cleaning, to prevent future buildup, while the
gel comes in a jar that is left uncapped while welding. Every so often, you take
the hot MIG gun and stick the nozzle directly into the gel, which leaves a coating
inside the hot nozzle and on the contact tube.

Shopping for a MIG welder
The array of available MIG machines aimed at the consumer and small shop
market has greatly increased in the past decade. Many automotive body workers
and fabricators in small shops used to dream of having a MIG welder to round
out their capabilities, but the machines available at that time were either very expensive self-contained MIG machines or wire-feeding attachments for alreadyexpensive, large-size arc/TIG power supplies found only in welding shops. The
hobbyist, auto body man or muffler shop couldn't justify the expense.
That changed when imported MIG machines started making their appearance in the US, aimed at the hobbyist market specifically. The companies advertised in hobbyist publications, attended auto enthusiast shows, and made a
presence in the business community. At first, the big domestic welding-equipment manufacturers took little notice, but after a few years they realized there
was a gap in their marketing and price structure and began to produce similar
equipment to gain back this emerging hobbyist/small shop interest in MIG weld-

5.12 Eastwood Company makes
these multi-function MIG pliers, which
can be used to clean nozzles, snip
wires, and hold contact tips to
unscrew them.

5.13 These three chemicals are
helpful in performing clean welds and
maintaining your MIG torch in good
condition. The anti-spatter spray and
gel are used on the nozzle to make
removal of debris easier, and the
weld-through coating by 3M is used
when welding high-strength steel in
late-model cars. Unlike the other
sprays, it is applied to the area to be
welded, providing extra corrosion
protection after the weld.

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5.14 The bigger and better
the machine, the more
expensive the internal
components. Sometimes
you can get an idea of the
relative complexity inside a
MIG machine by comparing
shipping weights when
shopping for a welder. The
more expensive ones are
generally much heavier. This
is the inside of a MIG 200
from HTP.

ing. Today there is a wide variety of machines offered from both domestic and
imported sources that run the gamut from very small, very portable units that can
be powered from a 3000-watt generator if necessary, to larger shop units with all
the "bells and whistles."
When the domestic manufacturers started competing with the imports for
the lower-price end of the MIG market, there was considerable talk at the local
welding supply level about how the imports weren't as good as the domestic machines and that anyone who bought the cheaper imports would have trouble later
on finding replacement parts. In the beginning of this marketing struggle, there
was some truth to this, but the competition of today's marketplace has pretty
much sorted these problems out. There are some very reputable companies selling imported MIG and Plasma machines, and most of them have a full line of
consumables and other replacement parts on hand.
As with automobiles, there will always be some debate on import vs. domestic, but today such distinctions are harder to draw than they used to be. Like our
cars, some domestic welding machines use components made overseas, and
some imported machines use American-made parts. As you shop for a MIG machine or plasma cutter, you may still find resistance to imported equipment at
your local welding shop. The answer is to listen to everyone, including especially
anyone you know who has purchased and used the equipment you are contemplating. Find out if they have ever needed parts or service for their equipment,
and did they have any problems with equipment under warranty. Be sure to compare the usage they put the equipment to, because there is a big difference between what is required in hours of welding on a daily basis in a shop, and your
needs of welding a project or two a few times a year.
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MIG welding
We have discussed duty-cycle comparisons in the previous chapter.
Most manufacturers give you a duty-cycle rating at the highest amperage
and the lowest amperage, and you may never have to use either one. If
you contemplate a machine with say 140-amp capacity, it may have a
duty-cycle rating of 95% at 30 amps and a 30% duty-cycle at its peak of
140 amps. The cycle relates to how many minutes out of a ten-minute period you can weld continuously without overheating the machine. At a
100% rating, you don't need to stop for anything, even if you are welding
long seams together. In most home/shop situations however, you are not
on a production schedule or a time-clock, and most of your joints will not
be long seams. Also, you will probably weld a seam, such as a corner joint
on a tubular framework for a utility trailer, that will take you only a minute
or less to weld up (doing one side at a time), then you will move to another
part of the project, perhaps set up some clamps or fixturing to ready the
next joint for welding, and all this time the machine is cooling off so you
may never exceed the duty-cycle even at higher amperages. This is where
the big difference in cost in MIG machines is. The heavier-duty, shop-type
machines have more expensive electrical components inside to handle a
higher duty-cycle (see illustration). You should buy as much duty-cycle
as you can afford to, but don't be too concerned that in your garage you'll
spend all your time sitting around waiting for the machine to cool off.
You'll find you will not often weld at the highest amperage output anyway,
and when you do, even a 30% duty-cycle is livable.
5.15 Sometimes a medium-size
There are two basic types of smaller MIG machines you'll be looking at, the
machine is all that is called for in a
gas-shielded type that uses bare electrode wire and a bottle of compressed gas,
particular shop, like this Miller 150
and the flux-core type that uses no shielding-gas bottle but has a special wire
used in a muffler shop, but the weldor
with a fluxed core inside that produces the shielding gasses as you weld, much
uses a large-sized shielding gas bottle
like the vaporizing coating on arc-welding rods. There are advantages and disadfor extra weld time. Note how this
weldor has added a tubing arm to the
vantages to each type, and your choice depends on the kind of work you will be
cart, to organize the cables and hold
doing. Most of the machines on the market are for use with bottled shielding-gas,
pliers and and-spatter gel.
and there are some units that can be equipped for either type of wire, in case you
have need for both. These machines cost a little more than single-use MIG machines because they have
to have a switching device
inside to change from reverse polarity (with the
torch being positive and the
work negative) which is required for the solid wire and
straight polarity (with the
torch negative) for the fluxcored wires.
The flux-cored wire machines do not make as
pretty a weld, if that is a
concern to you, and there is
some slag to be removed
afterward, though it is easier to remove than the slag
from arc-welding. With
some kinds of flux-cored
wire, the slag will peel off
5.17 A 110-V, 130-amp MIG is made by
5.16 A popular entry-level MIG machine is
the seam in strips. In body
this 110-V Pocket-MIG from Daytona MIG.
several companies for the home/shop
shop work, the extra thickmarket, this one is by Daytona MIG and welds
Though it weighs only 42 pounds, it has an
up to 5/16-inch steel. It features a cooling fan
amp range from 30-110 amps, capable of
ness of the flux-cored wire
welding up to 1/4-inch steel. Very portable,
and a 30% duty-cycle at maximum amperage,
may make them too hot for
it's ideal for home/shop use, especially on
95% at 30 amps.
light-gauge
sheet-metal
sheet
metal.
work. Some experts say
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Haynes Welding Manual

5.18 If you need the flexibility of welding indoors and out, a
combination MIG that uses either gas-shielding or flux-cored
wire fills the bill. This Combi 888 runs on 110V power, with
130-amp capacity.

5.19 There are small MIG machines that come
equipped for use with flux-cored wire, but have an
optional kit that can be attached to work with
shielding gas and solid wire. Eastwood Company's
wire-feeder uses 110V current, and has a 20% dutycycle at its maximum amperage of 85. It's fancooled and adequate for light-gauge welding.
that flux-core MIG welding is best suited for 18gauge or thicker metals, and most cars today are
using 22- to 24-gauge steel, except for 20-gauge
in areas like floor pans. Even replacement steel
patch panels for cars are seldom thicker than 20gauge. Virtually all of the newer cars are using
lighter-gauge metal of higher-rated alloy to reduce the overall weight of vehicles to meet
tougher fuel economy and emissions standards.
The main advantage of the flux-cored machines
are in outdoor or drafty situations where wind can
5.20 Eastwood's gas conversion kit for their MIG welder contains the
regulator, nozzle, tips and other parts to adapt a shielding-gas bottle to
blow away the shielding gas from a "bottle-fed"
their 85-amp welder.
machine, ruining the weld consistency. The fluxcored wire works well for fencing repairs, farm
equipment too big to be moved indoors, outsized
sculptures and similar projects. These machines also have the advantage of not
needing periodic refilling of gas bottles. As long as you have electricity and a
spare roll of wire, there's nothing for you to run out of halfway through a project
on a Sunday afternoon when you can't get your gas bottle refilled or exchanged.
The advantages of the bottle-fed machines are numerous, the primary benefit being the higher quality of weld and the ability to work on very thin materials
without burning through. With shielding gas, there is very little spatter, no slag,
and you can even weld body panels that are painted or rusty, though a cleaner
parent metal will always make a better weld and produce less hazard from
fumes. We have seen a big-rig repairman MIG-welding a new and painted fan
guard to a rusty truck radiator-support framework. The budget for the job didn't
allow for the time that would be spent in grinding and sanding all of the edges
clean - the truck had to be back on the road making money. The result wasn't
5-8

MIG welding

5.21 At the upper end of the 110V MIG scale are 140-amp
units like this one from HTP America. It weighs 135 pounds,
welds up to 1/4-inch steel, and has timing features such as
stitch-welding and spot-welding.

5.22 Above the 140-ampere range, you are into the 220V
category of MIG welders, with more features and higher duty
capacities. This is HTP's MIG 160, which can weld up to 5/16inch steel, has eight heat settings, and is suitable for street rod
shops, muffler shops, or farm use.

pretty, but it was more than strong enough for the application and a testament to
what can be done.
As far as running out of gas is concerned, this is an issue, but most
home/shop users handle this by just buying a bottle that is twice as big as they
think they need. There is, of course, a pair of gauges on the tank that indicate the
gas-flow going to the welder and the total pressure left in the bottle, so you
should know before any big project just how much welding time you have left.
Bigger shops just keep a spare bottle of gas on hand and switch if they run out,
then send the empty back to the gas supply company for refilling to become the
next spare.
Input current is the next consideration in shopping for a MIG machine.
There's a number of home-type machines that can be operated on standard
household 110V current, which negates the need for any rewiring of your shop
area and also makes them more portable in the sense that you can use one anywhere there is a source of standard power. However, any circuit used for a welding machine should be at least a 20-amp circuit, and, in the case of the bigger
110V machines, a 30-amp circuit is recommended. The 110V (it's confusing, but
household current is also referred to as 115-volt at times, but 110V and 115V are
the same) machines are available in power abilities with a range of 30 to 110
amps on the smallest home MIGs and a 30- to 140-amp range on the largest.
Most of these machines handle wire diameters from .023-inch to .035-inch,
though some of the imports are set up for metric wire sizes, which are close
enough to US sizes that you can always find replacement wire to suit them.
Above the 140-amp range in maximum power brings you into the bigger
shop-type machines that require 220V current input. Most of these machines
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Haynes Welding Manual

5.23 This 220V unit, the 181C from Daytona MIG,
offers settings from 20 amps for light sheet metal to
180 amps for heavier work, and has a spot-timer and
quick-disconnect torch. This is suitable for light
fabrication shops.
5.24 For welding up to 3/8-inch steel, a MIG like HTP's
MIG 200 will do the job. It has 24 heat settings, up to 200
amps, and is suitable for farm or ranch work, commercial
fabrication, or repeated automotive projects like building
trailers or engine stands.

have an upper limit of 250 amps, which is a lot, and they offer a 50% duty-cycle even at this high amperage. These
larger machines also offer more "bells and whistles" such
as larger wire spools, the ability to handle more different
wire sizes, wheels on the bottom of the machine as standard equipment and the capacity and bracketry to hold
larger bottles of shielding gas. Designed as they are for bigger jobs, these medium-size machines can handle wire diameters from .023-inch to .0625-inch (1/16-inch), which is
bigger than virtually any requirement you will have need for
5.25 This close-up of a commercially made street rod part
in your home shop unless you take up amateur bridge
has a thick steel ring MIG-welded in two places to a heavy
building. You will see these 250-amp MIG machines hard at
bracket for suspension mounting. This is a large bead from a
work in many shops today, from muffler businesses to
good-sized machine. Note how smooth and clean the weld is,
street rod shops, race-car shops and general steel fabricathe bead looks almost like one piece, rather than overlapping
tors.
puddles, and look at the backside of the part (at right) to see
Other options you may find on these mid-size mathe indications of penetration. A MIG is easy to learn, but it
chines are controls for timing various weld functions. If you
will takes lots of practice to make welds like this.
were regularly spot-welding long seams in sheet metal, you
could set one of these machines up with a special spotwelding nozzle which has a flat front face with cutouts on each side. You bring
such a nozzle directly in contact with the metal and pull the trigger. An adjustable
timer on the machine sets the weld time for a perfect spot-weld with little or no
crown or buildup to grind off later. Also, you can set one up to do stitch-welding
as well, where you join work with a series of spot welds that overlap. The welding

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MIG welding
machine has a stitch timer that turns the arc on, pauses, arcs, pauses, arcs, etc.
This stitch mode isn't used very often but is helpful in joining very thin materials
where there is a chance of burring through with continuous welding. In the stitch
mode (in which the pause time is variable at the machine), the pause time allows
the first puddle to solidify before the next puddle is made, reducing the overall
heat.
Mid-size MIG machines also offer more range of heat settings than the entrylevel MIGs. While the smaller machines may have four settings from their lowest
to their highest amperage, their bigger brothers may also have a "fine-power" adjustment knob, which essentially gives four more positions for each of the four
basic settings on the main amperage knob. So instead of four settings, you now
have a possible sixteen.
Adapters and special attachments offered on some machines include a
metal shrinker and a stud-welding attachment. The metal shrinker works to reduce high spots in sheet metal, much as you would do with an oxy-acetylene
torch, but without the flames and with very controlled heat. The basic principle is
to heat the center of the high spot (such as from having hammered out a dent
from the backside) to cherry-red, then quenching it with a
wet rag, which "shrinks" down the high spot of stretched
metal: The MIG shrinker attachment screws on in place of
your contact tube, the wire is pulled back inside the torch
(the wire isn't used) and the wire drive and gas flow are
disconnected. The shrinking tip is placed in contact with
the metal and the trigger pulled briefly, heating the high
spot.
The stud-welding attachment is another body-working tool that allows you to "spot-weld" small studs onto a
dented panel. These studs fit a special slide-hammer that
pulls on the studs to work the dent out without having to
drill holes in the body and use a screw-type puller as has
been traditional. The studs can be clipped and ground off
easily after the pulling is done. There is also a separate
stud-welding tool that operates on 110V current without
the need for the welding machine (see the Safety and
Shop Equipment chapter). Another stud-welding attach5.26 In exhaust system work, muffler shops deal with broken
ment is made to use a threaded stud as an "electrode"
and rusted-away manifold studs all the time. HTP has a
and fuse it in place of a worn-out stud in automotive work
special feature to their MIG 160 that repairs such problems.
(see illustrations).
First the old stud is cut off flush.

5.27 A special attachment to the MIG gun holds a hollow
replacement stud. When the arc is turned on for about four
seconds the wire feeds through the stud and welds it to
the old stub.

5.28 The new stud is now welded in place, with strength said
to be up to 85% as good as original. This feature is a real
time-saver for busy muffler businesses.

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Haynes Welding Manual
To go to the top level in MIG machinery, you are now talking about
very expensive professional welding machines with large, multi-purpose
power supplies. As mentioned in Chapter 2, the bigger welding machines
designed strictly for professional shops are often multi-purpose power supplies capable of high amperages which can be set up for Arc welding, TIG
and MIG, with any polarity required. The amateur user will never need the
high amperages or high duty-cycles of these top-level machines. To use the
big machines for MIG welding usually requires that a separate wire-feeding
accessory drive be set up, and, with the lower prices of today's MIG market,
the big shops prefer to just buy a separate MIG welder for those needs, using the large power supply just for TIG welding.

Choosing shielding gas

5.29 Spot-welding of sheet-metal panels is
easy with a MIG, even a small one. For large
panels, welds may be made through holes in
the top panel. Here a new door jamb has
been added to a 1932 Ford with a series of
small spot welds. So little weld is above the
surface that no strength is lost when the
area is ground for painting.

By now, you should have an idea of what level of MIG machine will suit
your purposes. If you are like most home/shop users who aren't going to be
welding every day, your needs may be best served by a typical, entry-level
140-amp, 110V MIG machine using shielding gas. You now have to choose
a shielding-gas bottle (not included with most MIG machines), some wire (a
small sample roll may be included with your machine), and the type of
shielding gas you want to use. This sounds like a lot of choices, but the field
is narrowed down by what kind of work you want to do and how often you
need to do it. In all cases, the choice of shielding gas and wire type must be
matched to the kind of material you will be welding.
Capacity of the gas bottle is important, and most first-time weldors
make the mistake of buying less capacity because the bottles are cheaper,
only to find themselves
someday working on a
project over a weekend
(when there is little

5.30 various size shielding-gas bottles are available for MIG setups.
Check with your welding supply store on how long each size might
last. Most home/shop users buy relatively small bottles because
they want portability in a small garage area.

5-12

5.31 The smallest bottles are 20 cubic-foot
capacity, and easily fit into even a small welding
cart like this. The bottle and regulator are totally
protected here. This is a good size if you only use
the welder infrequently, or on small projects.

MIG welding

5.32 Gas-shielded MIGs are not made for outdoor work, but
as long as you can keep the wind currents away, they work
fine. On this driveway utility-trailer project, pieces of plywood
are used as wind shields while welding.

5.33 Most of your welding with shielding gas can be done
best with a 75% argon/25% CO2 mixture, which is excellent
for cleanliness and penetration, and can be used on cast-iron
and stainless-steel as well.

chance of getting a bottle refilled) and they are out of gas. Gas bottles are available in sizes from 20 cubic feet to 40, 60, 80 and 125 cubic feet of gas. This
roughly translates into welding time of from four hours for the 20 cu.ft. bottles to
14-16 hours for the 125 cu.ft. when used on a small machine like the 140-amp
unit in our example. There's a number of factors involved in how long a particular
bottle may last under different welding conditions, so these are just rough guidelines. Every time you use your MIG machine, you should look at your tank gauge
to see how much more gas is left. You may even want to just lease a small cylinder of gas when your first get your machine just to see how long such a tank
would last you, and then buy a bigger one if you think you need it.
The small bottles fit nicely under a small welding cart, making for a very
portable arrangement for occasional home use (see illustration). The larger bottles are heavy and bulky, so you'll have to build a welding cart (most first-time
weldors' first project) that can accommodate one. Of course, bottles of compressed gas are dangerous, even if the gas is non-flammable, due to the pressures involved, and any welding gas bottle must be securely mounted with
chains or sturdy clamps. It's important to note that welding bottles for electric
welding machines should be ideally mounted in an insulated manner, such as
with rubber underneath and rubber hose over any restraining chains. This prevents the remote possibility of arcing against the cylinder, which could damage
it.
Next there is the choice of shielding gas to use. One of the widely used
shielding gasses for MIG work is plain carbon-dioxide, or CO2. While it is in the
bottle, CO2 is really an inert gas, but technically it turns into carbon monoxide
and oxygen under the intense heat of the arc process. The oxygen can combine
with other elements in the air and in the parent metal to form undesirable oxides.
Thus, plain CO2 will not usually result in as clean a weld as with other gasses, but
it is used often because it is the least expensive shielding gas for welding steel. It
will weld very fast, with good penetration, but you should use a welding wire that
contains deoxidizing elements to counteract the effect of pure CO2.
Argon is a versatile inert shielding gas that is often used by itself, or in combination with other gasses to produce certain weld characteristics. For instance,
welding of non-ferrous materials like aluminum is usually done with pure argon. It
makes for good penetration patterns and a concentrated arc.
To weld ferrous materials, like the mild steel we will use for most home/shop
projects, argon is usually mixed with another gas, or sometimes two other
gasses, to provide special characteristics. While there are some esoteric mix-

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Haynes Welding Manual
tures of gasses in different percentages for specific purposes, a mixture of 75%
argon and 25% C0 2 has become pretty much the standard for welding mild steel
with short-arc MIG machines with wire diameters of .035-inch or less (see illustration). This mixture, often abbreviated as C-25, is more expensive than the
plain CO2 but produces much less spatter and consistently better looking welds,
even on materials that exhibit minor rust or scale. It is what we would recommend for most of your welding needs. If you were doing a lot of thicker materials,
overhead or other out-of-position welding and pipe welding, you might use a 5050 mix of argon and CO2 which offers good wetting and bead shape without the
excessive fluidity that causes a bead to droop or fall when doing out-of-position
welding.
If you are working in a body shop, you might be interested in a mixture that
Airco calls Argoshield LG®, which stands for light gauge. It consists of mostly argon with small additions of CO2 and oxygen. The combination is designed for
metals down to 20-gauge, and produces good penetration, but with a smaller
weld bead than normal for less sheet-metal finishing, less spatter and smoke and
good arc starting. It is specifically formulated to work well on the thin, low-alloy
steels now used on auto sheet metal.
For welding of non-ferrous materials, either straight argon or mixtures of argon and helium are used in various combinations which provide higher heat to a
MIG arc. Usually, the thicker the material to be welded, the higher the percentage
of helium that is included in the mix, and the HE-75 gas, which is 25% argon and
75% helium is typically used in industry to weld thick aluminum.
If you were interested in welding stainless-steel, you can actually use the C25 gas we recommended above for mild steel, but a mixture of 90% helium,
7.5% argon and 2.5% CO2 is widely used in stainless-steel MIG welding because
it offers a higher heat for the normally sluggish weld puddle on stainless, as well
as offering good stability, penetration and resistance to corrosion.
If you have to pick just one type of gas, the C-25 works great on steel, can
be used on stainless-steel and is also useable on cast iron.

Choosing wire
The bare steel wires used in a bottled-shielding-gas MIG machine are all
variations of the same basic metal, with varying amounts of deoxidizers added
for different applications and shielding gasses. The most common deoxidizer is
silicon. Others added may be manganese, aluminum, titanium, or zirconium, with
nickel, chromium or molybdenum added to improve mechanical or corrosion-resistance properties. The welding wires with higher levels of deoxidizers generally
are better able to weld on rusty or unclean steel surfaces.
Most of the steel wires for MIG welding fall under a designation from the
American Welding Society (AWS) of E70S-something, with the last digit being the
particular variation. For instance, one of the most common wire specifications is
E70S-2, which is deoxidized, and makes a good weld with C-25 gas, even on
rusty steel. Its main drawback is that it lacks fluidity; the puddle doesn't want to
flow out width-wise and may not stick well in heavy materials.
The E70S-3 wire is one of the most common and least-expensive MIG wires
available, with more deoxidizers and a more fluid puddle that makes a wider
bead. It has been used successfully for years on cars, farm equipment and appliances.
Next up in terms of deoxidizer content is E70S-4, which is a medium-priced
wire suitable for almost all steel welding. It offers good fluidity and better arc
characteristics than E70S-3, but has slightly more spatter, and is used on structural steel, ships, piping and boiler vessels.
Probably the high-performance and higher-cost wire available is the E70S-6,
which has the highest level of silicon and manganese as deoxidizers. It is suitable
for welding almost all steels, from thin mild steel to 1/2-inch plate (in the appro-

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MIG welding

5.34 Inside the wire-drive portion of a typical small MIG
machine, this machine comes with a small wire roll such as at
lower right, but comes with an adapter to handle the larger
rolls such as in the machine. The small wire rolls are
inconvenient unless you do only small projects.

5.35 This is the drive section of a Daytona MIG wire-feed,
which has a place inside to store an extra small roll of wire,
good for keeping the spare clean if you occasionally switch to
another type of wire for specific needs. Arrow indicates the
knob for adjusting the wire roller tension.

priate wire diameter) and works with the most popular gas mixtures, offering
good puddle fluidity, too (see illustration). It is one of the few MIG wires that is
completely compatible with today's thin, low-alloy, high-strength body metal in
unibody cars.
L-Tec markets a wire meeting the AWS classification for ER70S-2, 3,4 and 6
that they call Easy Grind, which is designed specifically for auto body work. It is
said to require less skill to weld thin materials, and to have a reduced carbon
content that means easier grinding to prepare for filler and painting. Besides automobiles, it is also used in welding ductwork, metal cabinets, lawn furniture, and
is designed to be on metal as thin as 26-gauge with smaller MIG machines.
Non-ferrous metals, of course, require different wires. The basic rule of welding electrode selection is to choose a wire or electrode whose content is much
the same as the parent metal you are welding. In the case
of stainless-steel, it can be welded with the steel wire we
have recommended above, but for better corrosion resistance (the main reason for making something from stainless-steel in the first place) stainless-steel wire should be
used. There are various alloys of stainless-steel, but one of
the more common varieties is type 304, and the best wire
for MIG welding type 304 is called ER308, with variations of
increasing silicone content in ER308L and ER308LS.
For aluminum welding, you need aluminum wire. Again,
there are many alloy variations of aluminum, and several
metal blends in aluminum wire, but perhaps the best MIG
wire for aluminum is called ER5356, which has a chemical
content proven to work in most situations. Aluminum welding is more difficult than steel in many ways, and often the
exact alloy of the parent metal is impossible to determine,
unless you have bought a large enough piece at a metal
yard that is still factory marked as to its alloy and heat-treat.
5.36 Your welding supply store will have a variety of MIG
There are even some aluminum alloys which are considered
electrode wires to choose from. The E70S-6 wire at left is
one of the most popular. At right is L-TECs Easy-Grind
unweldable, like high-strength aluminum such as 7075-T6.
for body work.

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Haynes Welding Manual

5.37 When starting in a new roll of wire, keep a pair of pliers
on the end you take off the reel, or the wire can unroll
everywhere. Feed the wire through the guide and over the
drive roller.

5.38 The wire tension is adjusted with a knob, and proper
tension avoids wire-twisting problems inside the gun. The
wire should be able to slip when it needs to. Most machines
have a feature that allows you to retain the tension setting,
once set, by swinging the tension arm away when
changing wires.

Learning MIG welding
One of the attractions of MIG welding that has brought these machines into
the home/shop market is how easy they are to learn. With a little instruction, virtually anyone can be MIG welding with an hour's practice time. As with anything
else, the more you practice, the easier it will be and the better your welds, but
before you get overconfident about your MIG welds, try cutting apart a seam you
have made to check the penetration, and make the other tests (bending two buttwelded sample plates in a vise) we have previously described to see if the welds
you're making are as strong as they are good-looking.
To set up your MIG machine, the first step would be to read all the directions
and cautions in the instruction book that came with it. One of the few adjustments you will have to make initially is to put a roll of wire into the machine and
set the drive-roller tension. The wire unrolls from the reel through a guide and
over a motorized roller, which feeds the wire through another guide and into the
cable going to your torch. Lay your torch and cable out on the floor as straight as
possible. Mount the wire spool into the machine as per your directions, but be
careful when cutting the end of the wire which is usually bent over to lock it into a
hole in the side of the reel. There is winding tension on the wire and if the cut end
of the wire gets away from you, it can start unraveling all over the place. Don't cut
the end loose until you are ready to feed it.
Hold the cut end with some pliers or vise-grips and carefully file or sand the
cut end until it is smooth. A sharply-cut end may snag as it travels through the
cable or torch. Insert the end into the guide, loosen and swing away the wire-tension adjuster, and feed the wire over the groove in the drive roller and on into the
next guide, still holding the wire firmly (see illustration). Most machines are set
up to handle several sizes of wire, but you must be certain that you use the driveroller groove that is the right size for the wire you are using. Most rollers have two
sizes on them and can be turned around on their shaft to put the other size in line
with the wire. There will probably be an extra roller with other sizes on it that
comes with your machine.
When six inches or more of wire have been fed into the welding cable, put
the wire-tension adjuster back in place over the wire, keeping the wire centered
in the groove. Turn on the welder and put the wire-feed speed about one-quarter

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MIG welding

5.39 There are three choices in regulators for MIG shielding gas. The unit at right is
a single-gauge, economy unit which indicates only the line flow, not the total tank
pressure, at left is a dual-gauge unit that shows both, and in the center is the more
professional model that has a floating-ball flow meter easy to read from a distance.

of the way and pull the trigger. At this point, adjust the pressure on the wire tensioner until the rollers are feeding the wire, and then turn it 1/4-turn more. With
the nozzle and contact tube unscrewed from the end of your torch, keep the
torch cable straight and run the machine until the wire comes out of the torch.
Slip the correct-size contact tube over the wire, screw it in and attach the nozzle.
The final check on wire tension is to make sure the wire can "slip" if necessary. Eventually in your MIG practice, you will virtually weld the wire to the contact tube. When this happens, and you are still pulling the trigger, the machine
tries to feed more wire but it can't come out of the gun, so it jams up inside in
what is called a "birds nest." To prevent this, bend the wire to the side of your
torch and put the nozzle right against the shop floor, simulating a stuck wire.
While watching the drive mechanism inside the machine, pull the trigger. The
drive rollers should have just enough tension to always pull the wire through, but
not enough to prevent slippage in case of a jam. If your rollers do slip in this test,
you're set.
If yours is a flux-cored-wire machine, you are ready to weld, but for the
shielding-gas machines, you have to set up the bottle. With the bottle mounted
firmly on your cart, attach the regulator to the bottle and attach the reinforced
hose (should come with your machine) to the regulator with a hose clamp, connecting the gas to the machine. On some machines, a special adapter connects
the reinforced hose to a small plastic hose going into the machine. Keep the two
regulator gauges protected from impact, and always keep the gas valve turned
off when you are not using the machine. Some cylinder valves only seal well
when the valve is either fully off or fully on, so when your machine is on, turn the
cylinder valve all the way, not just a few turns. You can check any of your gas
connections for leaks using some soapy water solution. Bubbles indicate leaks.
Adjust your gas regulator to the proper flow rate (cubic-feet-per-hour rate, according to your instructions) for the material and wire you are working on. Note:
One gauge tells you the flow rate and the other tells you how much pressure is
still in the bottle. You can't read either one unless the cylinder valve is turned on,
so don't look at your bottle one day and notice that the tank gauge looks empty turn on the valve to really see what's left.
Now you're ready to practice. Select some 1/8-inch steel, set your amperage
according to the suggestions in your instructions, and set your wire speed a little

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Haynes Welding Manual

5.40 The basic MIG units have only a few power settings.
Your instruction sheet will tell you the recommended
thickness of metal for each setting, and a chart on the front of
the machine usually tells you the amperage and duty-cycle of
the settings. After some practice on different materials, you
will learn instinctively which settings work best for your work.

FORWARD METHOD

Gun tip inclination and the
direction of the weld can be
changed to match different
welding conditions

5.42 Of the two methods of gun travel
with MIG welding, beginners often like
to use the reverse or backhand
method because they can watch the
puddling action much better.

5-18

5.41 The wire speed has a lot to do with the heat and quality
of the weld. Generally when you have it right, the MIG
machine makes a very satisfying steady "sizzle" sound.
Practice by adjusting the feed high and gradually lowering it
until the sound and results are satisfactory. If you do
repetitive projects, write down the amperage and wire speed
settings that have worked for you.

higher than what's recommended. The wire speed is key to getting a good weld
with proper heat and penetration, and tuning the speed is easy. Listen to the
sound the welder is making as you make a straight bead. If the speed is too fast,
most of the wire coming out will be red-hot and there will be a loud crackling
noise, gradually adjust the speed down until you get a steady sizzling sound. The
wire should be melting right at the weld. Practice tuning in the wire speed at different power settings and metal thicknesses.
There are two torch-holding techniques for MIG welding, forehand and backhand (see illustration). The first is when the torch is angled and moved such that
the weld is taking place ahead of the torch's direction of travel, and the backhand is when the weld takes place behind the torch (see illustrations). Most beginner find the backhand (also called "dragging" the weld) technique works best
on most steel-welding projects, giving the weldor a better view of the puddling
action. In either style, the torch is angled about 35 degrees to the work. If you
find yourself doing a vertical seam, you can travel either up or down, but use the
forehand technique (sometimes called "pushing" the weld) only when going up,
and the backhand technique going down, keeping the arc on the puddle's leading edge at all times for good penetration.
After making good straight beads on top of the plate, try joining two plates. If
you are working with materials under 1/8-inch thick, most steels can be MIGwelded without beveling the edges, but you should tack the parts together with a
slight gap between them before finishing off the seam with a full weld. This assures good penetration. On 1/8-inch and thicker metals, the edges should be
beveled before tacking them. If you find that you are consistently burning through
the material, the heat setting is too high, or you are moving too slowly. If it is
"cold" appearing and not penetrating, the amperage may be too low, or you may
be traveling too fast. You will adjust your travel speed with the torch by watching
how the puddle develops, moving the torch along at a slow, steady rate. One of
the great advantages of the MIG process is that your torch is right down close to
the work, and there is much less intense light, heat and spatter as with arc-welding; you can get your head closer to the work to really see the puddle progress.
Keep a pair of sharp wire-cutting pliers on your welder at all times. You will use it
when you start each time to maintain about 1/2 inch of wire sticking out of the

MIG welding

5.43 The tip-to-work distance is very important in maintaining the
short-circuit arc. When practicing, watch the arc closely. The whitehot, melting end of the wire should stay about the same short
distance from the puddle. Wire speed and welding travel speed
control this.
5.44 This is what some of your practice welds will look
like. The heat setting was too hot here, and the weldor
wasn't very steady with the gun. Use both hands and
find a very comfortable position to hold it steady.
Note the amount of spatter from making and breaking
the arc.
5.45 This production weld by a
professional shows how clean and
perfect MIG welds should look. The
heat-affected area on either side is
small, the weld has good penetration,
and there is minimal spatter. Heat was
evenly played on both pieces of tubing.

5.46 Welding current affects the penetration of the weld and the size
of the bead. Ideally, you are looking for good penetration without a
too-tall or too-wide bead.

5.47 At left here is a MIG bead that was too low in
amperage for the thickness of the material.
Penetration is shallow and the bead sticks up too
high. At center, the correct amperage was used,
and at right, the amps were too high. The right-hand
bead may look OK here, but penetration was too
deep (dropthrough on the backside) and there was
some undercutting on either side of the bead.

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Haynes Welding Manual

OVERLAPPING BEADS
5.48 After you have practiced
sufficiently, you'll develop a natural
rhythm for the torch movements to
create a good bead of overlapping
oval puddles.

Insufficient penetration.
Weld strength is poor
and the panel could
separate when it is
finished with a grinder.

ARC VOLTAGE: LOW

INCORRECT

CORRECT

INCORRECT

Good penetration and
easy to grind.

ARC VOLTAGE: MEDIUM

There js good penetration
but finish grinding will be
both difficult and time
consuming.

ARC VOLTAGE: HIGH

5.49 Arc voltage and length affect the shape of the bead's profile and its penetration. Cut a few of your practice welds in half to
examine the beads. The shape of the overlapping puddles should have rounded ends exposed, not sharp, triangle ends.

5.50 The thickness of the panel you are working on
determines how far apart your initial tack-welds should
be to firmly align your parts. On thin materials, you need
a lot more tacks.

5-20

5.51 When working on large panels of thin material, such as when
doing body work like welding on a new quarter-panel, warpage is
a problem unless you keep the heat down by making lots of tack
welds, then switching back and forth to the coolest section to add
a short weld, then move to another section, and switch back and
forth until the whole seam is done. A continuous weld might put
too much heat in, and warp the new panel, requiring lots of
hammer-work to straighten.

MIG welding

5.52 Instead of a straight butt-weld, panels of thin material are
often joined with spot welds, in which the top panel is punched with
small holes. You MIG-weld around the hole, joining the top panel to
the bottom.

5.53 Door-handle and lock holes have been filled in
on this street rod door, using small circles of sheet
metal the same thickness as the original metal. In
order to avoid warping, the circles were filled by
tacking the filler pieces in a few places, waiting for
the part to cool off, then adding a few more tacks,
until the whole circle was made of tack welds.

gun. If you are welding thicker materials, or two edges that have irregular gaps, you can weave the arc back and forth from side to side as
you travel, bridging the distance between the two edges.
Sometimes a start-and-stop technique works well for bridging gaps or filling
holes. You watch the arc and weave from one side to the other, then pause (let
go of the trigger) for a second with the torch in the same spot, allowing the puddle to solidify, then pull the trigger again, building a new puddle onto the last one.
To fill a hole, just keep making tack-welds around the edge of the hole until you
have made it smaller (see illustration). Let the metal cool, then add an inner row
of tacks inside the first "ring" until you close up the hole with filler metal. This is
often done in filling sheet-metal holes in body work, but any hole larger than a
dime should be filled by welding in a circle of new metal of the same thickness.
The beauty of the MIG process is that the torch is a one-hand operation,
which allows you to use your other hand to steady your primary hand and draw a
smooth bead. Also the torch stays the same distance from the weld at all times,
unlike arc welding where the rod is always getting shorter.
MIG welding doesn't require stopping to change electrodes
either, so you can concentrate nicely on what you are doing. The one-handedness of MIG welding tempts some
weldors to operate the torch with one hand while they actually hold something on the work with their other hand. This
is OK for tack-welding, where you have a body panel you
need to hold in alignment while you tack, but better seams
are made when you hold the torch with both hands. Some
users get used to the lower brightness and spatter of the
MIG process, and are tempted to tack parts together without using a helmet. Body men in particular are prone to
hold two panels in alignment, put the torch where it needs
to be, close their eyes and make a tack weld for a second.
Although MIG welding does produce less intense light and
spatter than arc welding, you are still subject to both radiation burns and some spatter. Don't ever take a chance with
your eyesight. One blob of spatter onto your bare eyelid
5.54 When welding a corner joint such as a T-section, angle
could be really dangerous! A much better procedure (and
the gun at about a 45-degree angle to aim equal heat and filler
the only one we recommend) would be to use some clamps
on both pieces.
or other devices (see the Safety and Shop Equipment chap-

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Haynes Welding Manual

5.56 The best argon flow meters for professional use are the
type with a floating ball inside a glass tube. Every time you
pull the trigger, the ball floats up on the scale to indicate the
gas flow to the machine. At a normal working distance from
the machine, the weldor can more easily read this than a dial
gauge. It makes it easy to see at a glance if you forgot to turn
on the gas at all.
5.55 Don' be tempted by the low
spatter of MIG welding to just shut
your eyes when tacking body panels.
If you need speed and convenience
while tacking, use a hand-held safetyshield with lens as shown here.
Weldor here has long sleeves, but
should have gloves on and a turnedaround hat to protect his hair from
hot spatter.

ter) to hold your panels in alignment, and use a helmet. If you don't like the
bother of flipping a big helmet up and down to just make a series of quick tackwelds, then use a hand-held face shield with lens (see illustration). It's very easy
to hold the shield in your left hand while tacking with your right, and it goes instantly from shielded to an unshielded view of the work.
If you are welding along and all of a sudden the bead goes bad, there are
several things to consider. If you have been steady with your arc distance and
travel speed, then perhaps a draft temporarily blew the shielding gas away from
the weld. If it's not a draft, look to your main torch cable. If there are any bends or
kinks in it, in the position in which you hold it when welding, the flow of gas can
be restricted easily. Watch your gas bottle gauges while you pull the trigger for a
second to see if the flow rate has changed or if the gas bottle is running low. The
better equipped MIG machines in most shops have a type
of regulator with a flow meter to indicate the flow rate (see
illustration). It consists of a glass tube with a colored ball
inside that floats during gas flow. The numbered line it
floats to indicates the flow rate. The advantage of these
more expensive regulator/meter setups is that the weldor
can see the gas flow from where he is at the work. He doesn't have to go back to the machine to read a gauge dial.
Aluminum welding will be more of a challenge than
steel, regardless of the welding method used. Aluminum really soaks up heat, and you have to use thicker wire, and
more heat, wire and gas flow to weld it. Equipping your machine to weld aluminum means: setting the gas flow almost
twice as high as for steel, using aluminum wire, using the
right gas mix, replacing the wire liner in the torch with a
Teflon liner and using a contact tip that is one wire-size big5.57 When MIG-welding aluminum, especially thin aluminum,
ger than the aluminum wire. The reason for all this is that
the aluminum wire itself is fairly flexible, which can cause
the aluminum wire tends to grow more with heat than the
feeding problems inside the machine, because the drive
steel wire. The wire tension needs to be fairly light, because
rollers are pushing the soft wire a long distance. This is a
bird-nesting is more commonplace with the less stiff aluspool gun, which holds a small roll of aluminum wire right at
minum wire. In fact, there are special MIG guns made for
the gun for easy feeding.

5-22

MIG welding

5.58 For tight quarters such as muffler work and other roundtubing situations, HTP makes this MIG gun with a flexible swan
neck. It can even be used straight ahead, to reach into a spot where
you can't get your hands.

5.59 Muffler shops are finding that the MIG machine is
faster and safer to operate under a car than the
traditional oxy-acetylene torch equipment. There is no
constant re-lighting and adjusting of the flame to worry
about when initially tack-welding various pipe
sections together.

5.60 A handy welding cart for your MIG machine will probably be
one of your first home/shop projects. This one is simply-built from
one-inch angle-iron, fitted with a steel bottom shelf to hold the
welder, bottle and accessories, and the top was made from a piece
of polished-aluminum diamond plate purchased from a remnant pile
at a scrap yard. Caster wheels were added quickly by welding their
mounts to the bottom.

production work with thin aluminum wire that hold a spool of wire right at the
gun. Called spool guns, they eliminate the wire-feeding problems of trying to
push a soft aluminum wire all the way through a cable to your torch (see illustration).
The wire speed should be faster than for an equivalent sized steel wire, and
the forehand technique is recommend because it puts more preheat ahead of the
puddle. There are two extra steps in welding aluminum. The metal must be
scrupulously clean and preheated to 350° F to get a good weld. You should keep

5.61 You'll find many uses for your
welder once you get used to using it.
This example of a typical home
project is a plywood-covered rear
bumper extension for a truck. It's
used for carrying extra camping gear,
and used as a tailgate for working or
cooking when camping. Its also a
wide step when stepping out of a
camper shell on the truck.

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Haynes Welding Manual

5.62 The camper-step was MIG-welded from one-inch steel tubing
and braced to a 2x2-inch tube that fits into the truck's hitch receiver.

5.63 Street rod shops, customizers and restoration
shops are using a MIG welder more and more, for its
convenience and ability to handle delicate thin
materials. This 1932 Ford door has had a new skin
MIG-welded along the bottom where the original door
was rotted away.

5.64 The door bottom was welded on with a series of very short
welds, alternating from one area to another to keep from putting too
much heat at one time into an area. Eventually, the whole seam is
welded. L-TEC Easy-Grind deoxidized MIG wire is perfect for these
kinds of jobs, because it grinds off easier, without inducing too much
heat in preparing the seam for finishing and paint.

5.65 Customizers and restorers are fond of achieving a perfect gap
around body panels on first-class vehicles. Often this involves
grinding material off an edge or, as here, adding a sliver of metal
along the door edge (at right) to close up a gap. Welding these thin
strips is the perfect province of small MIG machines.

a stainless-steel wire brush handy that is strictly used for cleaning aluminum.
Don't use it for brushing steel or it will later on contaminate your next aluminum
weld.
Start welding aluminum with the torch further out than you would for steel,
say one inch. Always start an aluminum weld with the end of the wire cut off fresh
with snippers. As soon as the arc starts, move the torch closer, down 3/8 to 1/25-24

MIG welding
inch from the work. Instead of the torch angle we recommended for steel, hold
the gun almost square to the material and inclined only 5 to 15 degrees in the direction of travel.
The puddling will seem much different in aluminum than in steel. The puddle
freezes very fast, and the only change you notice is that the molten area is the
only place that is shiny. Aluminum has a narrow range of melting before it vaporizes and is highly susceptible to tiny amounts of foreign material. If you see black
specks appearing as you go along on a seam, they represent impurities coming
to the surface. The short-circuit type of MIG machines we have been discussing
are best when the aluminum being welded is relatively thin. Thicker parts are better welded with TIG equipment or the spray-arc-pattern found on larger industrial
MIG machines.
There will be a little more maintenance on the nozzle and contact tube when
welding aluminum, due to increased spatter. The use of an anti-spatter spray inside the nozzle, or dipping the hot gun tip in nozzle gel, won't produce any less
gunk inside the gun, but it will make its removal much easier, as it does with steel
welding. If you use an anti-spatter chemical, it can act as a contaminant to the
aluminum weld, so, after applying the anti-spatter, briefly use the torch on a
piece of scrap aluminum to "burn-in" the chemical so it won't drip off onto your
"good" weld.
One of the most common aluminum welding jobs in automotive work is repairing cracked cylinder heads, bellhousings and other large aluminum castings.
The cracks should be well ground out to virgin metal and Vee'd before welding.
These parts can really soak up heat so they should be thoroughly preheated, either in an oven or with an oxy-acetylene torch fitted with a rosebud tip. The oldtimer's method of measuring the preheat was to coat the part with black soot
from a overly-rich gas torch. Then with a torch set properly, the part was heated
until the soot burned off, and that was considered enough preheat. Obviously,
too much preheat could require complete re-machining of the part after the welding to correct warpage. Modern weldors use temperature marking sticks to get
an exact preheat.
Maintenance on your MIG equipment is simple, but should be performed
regularly to keep everything operating smoothly. The most often-maintained
items are the gun components. The contact tubes wear out from frequent use as
well as become burned such as when you hose kinks and the gas stops during a
weld. Sometimes the hot wire welds itself to the contact tip. Often the problem
can be fixed by filing on the end of the tip to free the wire's bond, or by pushing
the wire to the side with your cutting pliers. If not, you can remove the nozzle, unscrew the contact tip and cut off the wire. Then feed the wire through a new contact tip and screw the tip in place and replace the nozzle. Use anti-spatter agents
often, and clean out the nozzle and contact tip before starting a project, during
the project, and after the project. When you replace the roll of wire, use a blowgun on your air compressor hose to blow any dust out from inside the cabinet,
and blow off the roll of wire before you install it. Keep the drive rollers clean with
mineral spirits and lint-free cloth. Often professional weldors will tape piece of
lint-free cloth inside their MIG welder such that it drags across the wire as it
comes off the roll. The cloth helps to snatch any lint or dirt from the wire before it
can collect in your cable or torch.
That's about all there is to MIG maintenance. This is a welding system that
has really become the prominent method for the home/shop user in the last
decade, and if you have read all of the above, you can see why it has many advantages. Once you start using one, you'll really appreciate it. The lack of paraphernalia, the ease of starting and maintaining the arc, the cleanliness of the
welds, reduced shop fire hazards and the ability to weld various materials, including thin sheet metal, have combined to take the MIG process out of the exclusive hands of production weldors and give hobbyists, artists, farmers and
restoration technicians a very practical, easy-to-learn welding system.

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Haynes Welding Manual

5.66 It will take some practice to become competent with any welding equipment, but MIG is the easiest to learn and the most
forgiving in most automotive and home/shop applications. Test your practice welds for strength and cut them apart now and
again to compare with the illustrations shown in this MIG-welding troubleshooting chart.

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TIG welding
When those who are interested in welding talk about fusion techniques, the
subject of TIG welding is held in a certain reverence. Its reputation in this regard
partly stems from its place in history as the method used for construction of a
great many famous aircraft. Although developed initially in the 1920s, TIG (Tungsten Inert Gas welding) wasn't used much because the helium shielding gas was
too expensive. The intensified research atmosphere of W.W.II spurred further development as aircraft were being made lighter and lighter
and TIG became the preeminent method of joining such
non-ferrous materials as aluminum and magnesium. The
Linde Corporation (now L-TEC) was the first company to
capitalize on the technique, and after the war their trademark name "Heli-Arc" became the de facto generic name
for TIG welding. Many weldors today still use the term heliarc more often than TIG as a description of this type of
welding, even though a number of other companies have
been making TIG equipment for many years.
Besides the romantic beginnings, the TIG process has
been considered quite special for other reasons. It does
take considerable practice to be good at it, and, because
the equipment has always been rather expensive, a weldor
who had one and was good with it developed a reputation,
particularly in the field of esoteric materials and exotic construction in aircraft and race cars. Basically an outgrowth of

6.1 The TIG process is considered the most precise, most
controllable and cleanest method of welding. The arc is made
between the work and the central tungsten electrode in the
torch, while a flow of shielding gas comes in from the nozzle.
Note the low angle of filler rod addition. TIG or heli-arc
welding is also one of the most observable welding process,
with no spatter and little smoke.
6.2 Where the TIG process is unequaled is on non-ferrous
materials or on thin materials. Here a custom bicycle frame
was heli-arc-welded from very light, very thin-wall 4130
chrome-moly tubing for strength without a weight penalty. For
the same reasons, this kind of material and welding process
is use in race cars and aircraft.
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Haynes Welding Manual

6.3 Where welds on aluminum have to be as pretty as they
are strong, TIG is again the top choice. The weld on these two
machined and polished parts can easily be wire-brushed to
look as good as the polished parts.

6.4 Unlike arc-welding or MIG-welding, the weldor can get
very close to his work with heli-arc equipment. Even when
welding on this cast-aluminum dry-sump oil pan, smoke is
minimal and the arc not nearly as intense.

arc welding, the TIG process is done with a lightweight torch that uses a tungsten electrode to draw an intense, concentrated arc, shielded by an inert gas.
The gas comes out of the torch, all around the electrode and displaces the air
from the weld zone to exclude oxygen and nitrogen from contaminating the weld.
Although helium was the original gas used, today argon is the most common
shielding gas for TIG welding. The tungsten electrode is not considered a "consumable" in the usual sense, since filler metal is supplied by separate, hand-held
rods, much like in oxy-acetylene welding. In many ways, heli-arc welding is like a
high-tech version of the old-fashioned gas torch.
The concentrated nature of the TIG arc is one of its strong points. Welds of
great strength and quality can be made on thin materials, light materials, dissimilar materials, in fact most available metals, and all with minimal distortion or corruption of the adjoining base metal. The process does not generate sparks or
spatter, and the welds are as clean as can be, which is why it is the method of
choice in aircraft, race-car construction, and stainless and aluminum products
made for the medical, dental or food-handling services.
There is no slag involved, and, because there is very little
smoke generated, the weldor has a good view of the
process, allowing him to make very precise joints.
The weldor has greater control with TIG than most
other welding methods. The amperage control is infinite because, besides the settings on the power source, the weldor has a foot control he operates as he welds. We recently
asked a veteran weldor to make some sample TIG welds to
photograph for this book. There was to be one good bead
and several bad ones. Even when we set the amperage way
too high and way too low, he instinctively tried to produce a
good bead, adjusting his torch speed and foot control to
compensate. He couldn't make himself do a bad weld, and
once the arc was started he tried his best and made fairly
good welds even with the machine parameters way off.
With good torch manipulation, a TIG weldor can weld
6.5 Where precision welds are involved, especially in tight
thin materials to thick ones, steel to stainless steel, steel to
quarters such as on this stainless-steel race-car header,
cast iron, and enough other oddball situations that a good
TIG welding's wide range of operator control is seen as
TIG
weldor begins to be regarded as some kind of magian advantage.
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TIG welding

6.6 When thick-wall mild steel tubing is used in a race-car chassis,
welding is usually done with MIG equipment, because of its speed.
However, this chassis of lightweight, thinwall 4130 chrome-moly
tubing was TIG welded. There are a lot of man-hours represented here
in precisely-fit joints and welding time.

cian. In the time that we were in our friend's fabrication shop, he did a production
job heli-arc welding some aluminum brackets, some prototype motorcycle seat
frames, repaired a Lamborghini aluminum water-pump casting, welded up a
fancy cast-aluminum mailbox post that had been run over, and finally a gunsmith
brought in a trigger and barrel from an antique cavalry carbine to be repaired with
TIG-welding. He handled them all with equal aplomb, and it was obvious that
people from all around brought the tough jobs to him knowing he could handle it.
We've discussed many types of welding systems to this point, and each has
been shown to have its advantages and disadvantages. With TIG welding there
are only few disadvantages. There are very few jobs a TIG welder can't do, but
there are some jobs other techniques are better suited to for practical reasons,
not because of a difference in quality or strength of weld. For big jobs, like welding up a car trailer or a big metals rack made from steel tubing, the heli-arc is just
too slow - an arc welder or MIG would be much faster. However, there are applications in aircraft and race-car chassis work where a large project may be tediously done with a heli-arc, simply because a lightweight, high-strength material
like thinwall 4130 chrome-moly tubing is used where TIG would be the preferred
method (see illustration). For outdoor work, again an arc welder or flux-corewire MIG are the best choices because they aren't as affected by air currents.
The cost and complexity of the TIG system has kept it out of the hands of
most small shops until the last few years. Most large TIG setups are heavy, some
weigh up to 800 pounds and have to be moved with a crane or hydraulic palletjack, and most professional units have a water-cooled torch assembly which often involves some plumbing connections in the shop beside the normal electrical
hookups (see illustration). So the big shop-type TIG machines have always
been about the most expensive welding machines available, which has increased
their mystique but not widened their market. In the last few years, however, manufacturers have built smaller and lighter, solid-state-electronic TIG machines to
make them more attractive to the small fabrication shop, race-car shops and
street rod builders. Many of these machines are now air cooled, and, at about
one-third the cost of the traditional TIG machines, they are being seen out in the
field more and more. As one street rod builder told us, "There isn't a thing on a
car that would require me to have a 600-amp welder, and when you design and
build a car two brackets at a time, the torch never gets that hot."
That is the main difference between the usage of the large, industrial TIG

6.7 Most shop-type TIG welders are
heavy, bulky power sources that
require three-phase input power and
water connections, making them less
portable than other welding machines.
This is a Miller Synchrowave 250, a
popular unit in many fabrication and
race-car shops.

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6.8 The basic TIG torch is very light, easy to hold comfortably,
and quite durable. The only "consumable" is the filler rods, if
used, and to some extent the tungstens.

6.9 The exploded view of the typical TIG torch shows the
tungsten (right) and from top to bottom: the back cap, collet,
collet-chuck, torch body, and ceramic cup or nozzle. To
assemble, the collet-chuck is screwed into the torch body on
the bottom, the nozzle is screwed in on the bottom, the collet
slides in from the top, and then the tungsten is slid in and
retained by the back cap.

welding machines and the "economy" TIGs on the market today. The big boys
can weld all day long at any amperage they need and never overheat the torch or
the electronics, the air-cooled smaller TIGs are fine for anything but long seams
or welding big aluminum castings.

The equipment
The basic components of the TIG setup include the power supply, foot control, water circulation system and the torch. The latter differs from the other types
of electric-welding torches by being smaller and lighter and holding a central rod
of tungsten as the electrode for the arc (see illustration). Taking the torch apart,
there is a ceramic shield at the business end (called the ceramic, the gas cup or
the nozzle), then the collet, which retains the tungsten in the collet body, and the
back cap (see illustration). There is customization of the torch, depending on
the work to be done, in that there are different-sized tungstens, different gas
cups with shapes for specific kinds of jobs and different back cap lengths depending on how tight the quarters are where the weld has to be made. For instance, you could use a short tungsten and short back cap to fit into a tight corner better. The shape of the gas cup can create a different shape and size
envelope of shielding gas over the weld area. From the larger welding-machine
companies, there's a variety of different-size torch bodies with different amperage capacities as well as some special models made for tight confines, including
one in which the tungsten and ceramic nozzle come straight out of the handle
rather than at an angle like most TIG or MIG torches.
When it comes to the basic power supply, you will not find as great a range
of choices as with say, MIG welders. The marketplace for TIG equipment is still
pretty much a professional arena, and the newer, less-expensive air-cooled TIGs
are at one end, and the big, shop units are at the other, with few choices in the
middle. A TIG setup is still not a home/shop type welding process, though there
are certainly some small specialty fabrication businesses run out of a home
garage that could utilize a TIG machine, particularly if the work involved aluminum, stainless steel or other non-ferrous parts, and high-quality, squeakyclean welds were important to the products' strength or appearance. If you had a
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6.10 There are only a few small, more-portable TIG units, like this
100-amp "pulse-TIG" from Daytona MIG. It is a 220V, DC-only
machine, but is said to be suitable for steel, stainless-steel and
chrome-moly up to 3/16-inch thick.

small business making stainless-steel rope clips or other items
for rock climbers, for instance, you might weigh the cost of an
6.11 Mid-size TIG machines are in the 160-250 amp
air-cooled TIG versus sending all your parts out to be welded in a
range, though this fairly-portable Daytona MIG unit is
shop. If you had the volume of work to justify the one-time costs
130-amp, 220V. Mid-range machines offer options like
and the learning process, it could be a good move to do your
slope control and post-flow. This one has square-wave
own. However, it would be a wise move to take some TIG classes
technology, and AC/DC operation.
and get yourself certified first.
Input voltage on TIG machines begins in the 220V range of
single-phase power, and the bigger professional boxes are for 460V three-phase.
The professional units range in amperage capacity from 250 amps to 300, 400,
500, and 650, though the larger ones are multi-technique machines on which the
high amperages are probably used only on the arc-welding process. It would be
pretty rare to use more than 300 amps on a TIG weld, unless you had to weld really thick aluminum plates or castings. When welding at 300 amps or more, tiny
bits of the tungsten electrode can come off and become included in the weld,
which would weaken the joint. The three-phase current models are definitely for
shop use only, where the amount of shop equipment and power used every
month makes the expense of transformers and rewiring the building economical
over the long run in utility bills. Home shops generally do not have three-phase
power.
On the small-shop scale, there are very few TIG-capable units in the 115V
range. One we have seen is the Hobart Ultra-Weld 130, which is an arc-welder
with TIG capability, but with a limited range for either. In its 115V version, it offers
75 amp capacity with a 40% duty-cycle, and the 220V model offers 130 amps at
60% duty-cycle. It does not include the TIG torch, and its TIG range of material
thicknesses would be limited. We expect that as the home TIG market expands,
there may be some interesting, smaller 115V and 220V units to come. A few imported TIG units are built with DC-only capability to keep the price down to a
starter level, and they are fine for steel (only) up to 3/16-inch (see illustration).
Of the medium-range TIG units, there are several of the domestic and imported brands offered in the 160-250-amp category that can handle virtually anything in the small shop environment (see illustration). Most of these are 220V or
more in input current requirement, but most are single-phase, which means you
could easily wire your shop to accommodate them. Be advised though, that even
the 160 amp units can draw 36 amps of input power at their highest settings, and
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Haynes Welding Manual
the 250-amp machines can draw 60 amps or better on full load. This
means that your household 30-amp 220V circuit would blow at any of the
higher settings. You would really need a separate circuit and box for the
welder, with a 50-amp breaker for the smaller mid-range machines and
100-amp breaker for the bigger ones.
The mid-range machines offer several special features, such as
slope control (see illustration). This refers to how the wave of current cycles when the machine is welding. Picture the wave as a curved line that
goes up, down, crosses the baseline and then curves back up and over
again in repeated fashion many times a second. This is called a sinusoidal wave in alternating current. TIG machines use both AC and DC
current, with the AC used for non-ferrous metals like aluminum or magnesium. One half of the AC wave is actually straight polarity, and the
other half is reverse polarity. The straight-polarity portion of the wave
builds the heat in the arc, while the reverse current has the effect of
cleaning the oxides from the aluminum being welded. So the TIG torch on
AC is constantly cycling between a hot arc and a cleaning cycle, but at
lower amperages the arc can be obstructed at the changeover point or
actually go out. Most of the TIG machines have a special circuit inside
that produces a high-frequency, low-power extra current that keeps the
process going at all times. The high-frequency control makes the TIG arc
easy to start without touching the tungsten to the work, and makes a
more stable arc while welding. On many machines the high-frequency
6.12 When you go up in welding machine size,
system can be set on the front panel of the welder to arc starting, off, or
you get more amperage and higher duty
continuous use. On ferrous metal welding, the high frequency is used
cycles. This TIG-Star 250 operates on several
single-phase input currents, and has a 60%
mainly for arc starting.
duty-cycle at 200 amps, with 100% duty-cycle
The slope control is a feature in which the weldor can adjust the paat 140 amps.
rameters of the wave on the up side or the down side to
get the perfect combination of penetration and cleaning
action on aluminum. Even a clean piece of aluminum
contains some aluminum oxides in the base material,
and the slope adjustments allow a good weld to be
made without these oxides being included in the bead.
Most of today's TIG machines offer square-wave AC.
The traditional sinusoidal wave with high-frequency
over it creates a lot of radio interference as well as
some problems on welding aluminum (see
illustration). The new machines are all solid-state electronics, with features that make a wave made of up and
down squares, rather than half-circles. This means the
high-frequency control intervenes less often, and the
same-sized electrode can be used at higher currents.
This discussion of the current waves may be more than
the home/shop user needs to know, but at least you
may better understand the language used by manufacturers to describe their equipment. Suffice it to say that
the modern square-wave technology and solid-state
electronics are desirable features in a full-on TIG machine.
Another feature you may see mentioned is post-flow.
When you are making a bead and get to the end of your
6.13 As a standard "sinusoidal" wave of AC current flows, it is
seam it's a good idea to allow gas to flow over the end
constantly reversing its polarity and its output is always
of the weld as it cools, to keep out contaminants. On
fluctuating as the wave flows. With the new square-wave
most professional machines, there is an adjustable
technology, electrodes can be used at higher currents and have
timer that allows gas to flow for so many seconds after
good arc staring and stability, but without the radio interference of
you have stepped off the foot control to quit the arc.
traditional high-frequency superimposition. The square-wave
You keep the torch in place just where you stopped,
design inverts the current much faster, for better welds on nonand gas keeps flowing for the specified time. This is
ferrous materials.
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6.14 Less expensive, air-cooledtorch TIG machines have been
available now for some time and
are making inroads into shops
where TIG was previously
considered too expensive. This
Miller "Econo-TIG" is being used
in a street-rod shop on a homebuilt cart to make it as portable
as any MIG machine.
6.15 Today's state-of-the-art in
TIG machines is represented by
this 300-amp Heli-arc 306 by LTEC (the new name for Linde
Corporation, the original
trademark-holders of the name
heli-arc). All solid-state with
square-wave technology, it
provides high performance and
high reliability. The bells and
whistles include: slope control,
spot-weld control, wave balance
control, post-flow, and an "arc
force" fine-tuning adjustment.

helpful on steel, but is essential on aluminum, magnesium and brittle, highstrength steels like the 4130 used in aircraft and race-car construction. It's
called post-flow because it is post-welding gas flow. The post-flow of water
and gas to the TIG torch also helps to cool the tungsten electrode down to the
point where it can't oxidize when regular shop air flows around it after the welding stops.
Most shop-type TIG machines feature a water-cooled torch, but some are
air cooled, with the water-cooling system as an option (see illustration). Obviously, the extra equipment for a water-cooled torch adds
to the total price of the package. In some shops, the water-cooling
system consist of a unit added on to the basic power supply, containing 1-5 gallons of water, a water-circulating pump and a small radiator and fan. It's like a miniature automotive cooling system. In
shops where the amperages used can be quite high, or where long
welds are made, the torch may be hooked to a source of regular cold
tap water, and the heated return water flows back into the shop's
drain. This system uses more water, but keeps the torch cooler than
recirculated water systems (see illustration).
The shielding-gas system for TIG welding isn't much different
than for MIG welding, as discussed in the last chapter, except that
you will use helium, argon or a mixture of the two in your bottle. Most
TIG setups use as large a bottle as possible because portability isn't
usually a concern in TIG welding (see illustration). Shops that do
TIG welding usually have the machine set up right near their welding
table and don't move them around, although the newer air-cooled
units can be wheeled around a shop without too much trouble.
6.16 Argon bottles are available in a number of
Unlike oxy-acetylene bottles or most MIG-welding gas bottles
sizes, depending on whether you are trying to make
that use two-gauge regulators, TIG setups have a single round-faced
your TIG setup portable or not, and how much
gauge on their tank and a flow meter instead of the other gauge for
welding time you need. Shown here, from left, the
the line flow. The flow meter has a vertical glass tube with numbered
sizes are: 20, 55, 80, 125, 154 and 248 cubic foot.
increments marked on it and a colored ball inside. When the gas is
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Haynes Welding Manual

6.18 Argon is versatile enough to be used as the shielding gas for almost all
TIG work, simplifying the storage of bottles. Often one large bottle mounted
on a welding cart is all that's needed in most smaller shops.

6.17 Flow-meters for argon bottles in
TIG use are generally used in place of
twin-gauge setups. Inside the glass
tube on top is a colored ball that
floats along a measured scale to
indicate gas flow, but without
requiring the weldor to step away
from his work.

turned on and you click your foot-control on, the ball will float up inside the tube,
indicating the level of gas flow in cubic feet of gas per hour (see illustration).
Professional weldors like the flow meter better than a gauge because that colored ball can be seen floating in the tube from as far away as their welding table
- they don't have to get up and look at the face of a gauge on the tank. They can
just step on the pedal to start gas flow and see if the flow meter is set right. They
can also tell if they have forgotten to turn on the gas bottle before starting.
The correct gas flow is very important in maintaining the integrity of the weld
by keeping out contaminants. For most basic steels, a flow rate of 8-10 cubic
feet per hour with argon is sufficient up to 1/8-inch material, but the gas flow requirements go up with the amperage used and the thickness of the metal being
welded. Stainless-steel requires only a little more gas flow than for plain steel,
but if you were welding aluminum, the gas flow recommendation would go up to
15-20 CFH for the same thicknesses, and a larger-diameter tungsten may be required.
Argon is certainly the basic, all-around shielding gas for the TIG process today, and is useable on virtually all metals (see illustration). Straight helium is seldom used, but often in production work a mixture of argon and helium is used to
get the best properties of both gasses. Argon has the qualities of good arc-starting, cleaning action and best puddle control, while helium makes for a hotter
weld for greater penetration and a faster welding speed, such as when welding
thicker materials. An argon-helium mix is often used to allow welding of non-ferrous metals at higher speeds. The helium in the mix helps make more heat for
aluminum welding in a way that one weldor described as like "adding on a turbocharger."

The process in action
Basically, TIG welding is enough like oxy-acetylene welding that if you have
already learned well how to weld with a gas torch, the learning curve for TIG
welding will be much shorter than for most other weldors who have never learned
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TIG welding

6.19 Finding a comfortable position for your torch hand is more than
half the battle in achieving steadiness with TIG welding. Practice
making a bead on your proposed setup without turning on the arc, just
to find a comfortable position. Note the low angle and position of the
filler rod in the weldor's left hand.
6.20 This is a TIG welder of some years back.
Today's current crop of TIGs are half this size. The
water-cooling unit here is mounted on top, and at left
is a rack of metal tubing holding various welding
rods. The foot-pedal amperage control is in front.

6.21 Layout of this front panel is
typical of most TIG power sources,
with controls for coarse and fine
amperage, current type, highfrequency control and post-timing.

with a torch. It can be as challenging as it is rewarding. Like gas welding, the operator must use both hands, one for the torch and one for the filler rod, each of
which must be moved along the weld seam at the same, steady rate (see illustration). In addition, the TIG weldor has to operate a foot-pedal-controlled or
hand-controlled amperage device (usually clamped directly to the torch body)
that is remote from the welding machine (see illustration). Using the remote
control is one of the operator privileges of the TIG process, allowing the weldor
to start an arc, infinitely vary the welding current as he is welding, and end the arc
without moving the torch. Being able to vary the amperage while making a weld
is what makes TIG welding so versatile in handling different thicknesses of metals and the joining of dissimilar metals. Just the right amount of heat can be
aimed at each side of a joint, and this also helps make TIG a technique that can
work for all positions of welding, too.
TIG machines produce either AC output with high-frequency over it (HFAC)
or DC with the high-frequency for arc starting only (see illustration). Most TIG
machines have a control on the front panel that switches between the types of

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6.22 The three-position switch at left is for the highfrequency, and at right is the post-flow timing as related to
various sizes of tungstens. The bigger the tungsten, the more
post-flow timing to cool it off.

6.23 The lever at left on this Miller TIG sets the polarity, while
the right lever is the coarse amperage, with a bottom setting
of 10-55 amps, a medium range of 40-190, and a top range of
125-310 amps. Within each range, the fine-amperage knob
sets the upper limit for the pedal.

current, a control to select the basic amp range and controls for high-frequency
and post-flow (see illustration).
The AC is used on non-ferrous metals and usually has the high frequency on
during welding, except for the newer square-wave machines that don't require
high frequency all the time. The DC current can be either straight polarity or reverse polarity. The straight polarity (DCSP) is used for steel, stainless-steel, silver, silicon copper, brass alloys, cast iron, deoxidized copper and titanium, with
the AC mainly for aluminum and magnesium.
Set your Machine to DCSP (sometimes marked DC-), the high-frequency to
the start-only position, and set the amperage for the material you are working on.
Experienced TIG weldors usually set the three-position amperage lever as a
coarse adjustment, then dial in the fine amperage control with a knob (see illustration). Often weldors will set the fine control all the way up, using their pedal as
the ultimate control. That way, if during the welding the weldor needs a little more heat, he just puts the pedal down
further. Whatever you set as the limit on the fine-amperage
knob, that's as much as you can get from the pedal (see illustration).
There should be a chart with your machine that tells
you the correct size tungsten electrode to use with various
amperages and material thicknesses. You will probably use
a 1/16-inch, 3/32-inch or 1/8-inch for almost everything you
do. There are two basic kinds of tungsten materials, pure
tungsten or thoriated tungsten. The pure tungsten works
under all conditions and metals, but is required for AC TIG,
while the thoriated tungstens for DCSP welding are used
often because they make slightly better starts and penetration.
Tungstens are somewhat expensive, but can be made
to last a long time (see illustration). The sharpness of the
tip is important to good arc starting and penetration on
6.24 The pedal is the final weldor control of the amperage in
steels, so TIG weldors keep a small supply of sharpened
TIG welding. Until you are experienced, you may want to set
the amperage knob at the highest you need for a particular
electrodes handy to slip into the torch (see illustration).
job, and know that when you are welding, the pedal can go all
Most weldors will sharpen both ends of a tungsten, so that
the way. It takes some experience to know how much pedal
if they need a new point right away they just loosen the
to give, if the knob is set to the max for the amp range on the
back cap on the torch, slide the tungsten out and reinsert it
coarse adjustment.
with the new point down. Good weldors can do this in a

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6.25 Make the most of expensive tungsten electrodes by
using them until they are too short to fit the torch'. Shorter
tungstens can be safely sharpened without burning your
fingers, using a tungsten-holder like this.

6.26 Spare, sharpened tungstens

blink of an eye. A belt sander or grinder is usually used for sharpening tungstens,
should be kept handy. This is a TIG
but it should be a dedicated sharpening source (see illustration). A grinder used
caddy, which holds extra tungstens as
well as spares for all your torch parts
for smoothing steel or aluminum will have deposits on it that can contaminate the
and different size collets and nozzles.
tungsten. Sharpen the tip (like sharpening a pencil) only by grinding lengthwise
The caddy is magnetic, and features a
on the electrode, grinding from the tip back to the main body. Grinding it held
convenient torch rest.
sideways to the grinder will leave a pattern of marks on the
tip that may contribute to arc scattering. Electrode tips for
use on aluminum with HFAC should be sharpened to be
clean but with a much duller point than used for steel (see
illustration). Theoretically, you should have separate ceramic cups for aluminum work too, but many weldors do
use the same cup for both steel and aluminum TIG welding.
When tightening the electrode in the torch, push the whole
torch straight down against a solid surface (with the welder
off) to see if the tungsten will slide in. If it slides, the tungsten wasn't tightened enough (see illustration).
At some point, your tungsten tip will contact the puddle, this isn't desirable, but it happens to everyone. Pull the
pedal back all the way to break the arc, and keep the tungsten in the gas flow for a few seconds until it cools off a little. You cannot continue to weld with this tungsten after it
has touched either the filler rod or the puddle because it will
6.27 It's important to sharpen tungstens lengthwise on the
tip, so as not to leave any radial grinding marks that could
cause arc scatter. Grind points for steel like a pencil, like a
crayon for welding aluminum.

6.28 The tungsten at bottom has been sharpened for use on
steel, while the top one is for aluminum, with a small ballshape on the end. In theory, you could create a ball-end like
this by striking an arc on a piece of copper before using the
tungsten on aluminum, but a suitably-dull point will turn into a
ball like this with a few seconds use on HFAC for aluminum.

6.29 The sharpened tungsten is inserted into the torch body,
and when the tip is sticking out the right distance, you tighten
the back cap to hold it in place.

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6.30 Although you can crank up the gas flow and extend the
tungsten tip out further for reaching into a tight corner, the
normal extension of the tip should be 1/8-inch to 3/16-inch
from the end of the nozzle.

6.32 This is the backside of the
same plate as the previous welds.
Note how A has only a slight
discoloration, B is close to being
right, with a tiny bit of
dropthrough, and C is too hot, with
lots of dropthrough, while D is so
hot there's more bead underneath
than on top.

6-12

6.31 You'll make a lot of practice beads while learning to TIG
weld. Here at left we have: A, a bead with too low an
amperage, the bead sits up proud, B, the current control
seems about right., C, the amperage is set a little too hot even
though the bead seems OK on top, and D. way too hot, with
the bead too wide and sunken.

be contaminated, and the arc won't be clean and steady.
The blackened and pitted section of the tungsten will have
to be broken off with a pair of pliers, and the tip will need to
be re-sharpened. Although tungstens are not considered
consumable in the normal sense of the welding term, they
do get shorter every time you break off a piece and every
time you re-sharpen them, so eventually they become too
short to use. When welding in tight corners, a short back
cap can be used with a stubby tungsten, but otherwise use
a long cap to protect you from contact with either a sharpened tip (when you have sharpened both ends) sticking out
or a hot tungsten. The long back cap covers even a fulllength new tungsten.
Turn on your gas and set the flow to 10 CFH, attach the
work-lead to a sample plate and run some practice beads. The tungsten should
be held in the torch such that 1/8 to 3/16-inch of tungsten extends out past the
ceramic cup (see illustration). At no time should the tungsten touch the work.
When you bring the electrode to within about 1/8-inch of the work and hit the
foot pedal, the arc should start and there will be a red-orange glow at the tip of
the tungsten. As you move the tip around in small circle in one spot with the
torch perpendicular to the work, bring the pedal control down for more amperage. When the puddle is a bright fluid, move the torch along your seam slowly
and evenly. The torch should now be tilted back to a 75-degree angle for the rest
of the bead. To stop the process for any reason, just back off the foot control all
the way to break the arc, but keep the torch over the same spot to cool the weld
and tungsten with gas flow.
When adding filler rod as in most joints of any thickness other than thin sheet
metal, move the electrode to the rear of the puddle and dip the filler rod to the
forward edge of the puddle. Then bring the torch to the front again and make a
new puddle, move back, add filler, move again. This may sound like too much
work, but really it is very similar to gas-torch welding and the movements become instinctive after enough practice. The filler rod should not touch the electrode, and it should be kept near the forward edge of the seam to keep it hot be-

TIG welding
tween "dips." When it is brought to the molten leading edge of the puddle, a drop
of molten steel will come off the rod into the puddle and be blended in when the
torch advances over it. The filler rod is usually aligned with the direction of weld
travel and held down to a shallow angle with the work.
The rate at which you travel will depend on the thickness of the material you
are working on, the amperage and the desired height and width of the bead. If
you are too cold with the amperage or travel too fast, the bead will tend to stand
up more, and even if it looks smooth and uniform, the weld won't pass a bending
test because of lack of penetration (see illustrations). If you are too hot or moving too slowly, the bead will settle into the parent metal and leave a long crater or
at least some undercut on either side. On metals thicker than 1/8-inch, the edges
of the parts should be beveled, and you will probably make more than one pass.
The bottom pass or root pass ties the pieces together, and subsequent passes
can be made at a higher amperage. TIG welding is not a process that quickly fills
in large gaps or beveled seams on thick plates. MIG or arc welding is better for
that.
The filler rods used for TIG welding may look exactly like those for gas welding, but they aren't. The TIG rods for steel welding have deoxidizers added, in
fact one brand calls theirs "triple-deoxidized," and if you accidentally use a gas
welding rod, you can make a bead but the weld will exhibit porosity. The proper
TIG rods are very helpful when welding low-quality steels, which may be the
"hot-rolled" steel you find at the salvage pile at your local metal supply. There are
a variety of filler rods, including special blends used for the low-alloy, highstrength sheet metals now used in automobiles.
After welding, your tungsten tips should be silvery and relatively clean. If they
show signs of contamination, or are rough to touch, it usually indicates that air is
leaking in somewhere in the torch or that shielding gas is leaking out somewhere.
Check the cables and the fit of the collet and ceramic cup. If the electrode looks
like it has a ball on the end like a miniature flagpole, then the amperage may be
too high for that diameter of electrode. The tungsten shouldn't have a ball on the
end bigger than 1.5 times the diameter of the electrode itself. If the tungsten tip is
black or blue, check the timing of the post-flow on your machine. If the tip is
black, it means the tungsten is cooling off in atmosphere instead of shielding gas
and you need a little more time on the post-flow setting.
Look at the inside of your ceramic cup after welding and check it for contamination. A cup that is too small for the work will show deterioration and even
cracking. Cups are usually sized in 1/16-inch increments. A #4 nozzle is four-sixteenths or 1/4-inch, a #8 is 1/2-inch. The general rule is for the size of the cup to
measure 4-6 times the size of the electrode being used.
Your practice time before obtaining suitable beads will vary with your skill
and previous welding experience. As we have said, the similarities between TIG
welding and oxy-acetylene gas welding are such that you can pick-up TIG welding much faster if you are already an accomplished gas weldor. When you have
practiced straight beads and flat, butt welds and have those down fairly well,
then try some corner or Tee welds, and then vertical seams. When you are comfortable on these more difficult welds and the pieces you have done pass simple
bending tests and cutaways to examine the penetration, you may be ready to do
some actual projects with a TIG welder, but don't start right away with something
critical like an automotive suspension or steering part, or anything that goes on
an airplane.

TIG-welding aluminum
Perhaps a little more difficult to learn than welding steel, precision joints in
aluminum or magnesium are among the primary reasons for having a TIG welder,
so this should be your next area of practice.
You need a well lighted area to do TIG welding because the arc is not as

6-13

Haynes Welding Manual
bright as with other electric arc techniques, and on aluminum you really need to
see how the puddle is developing. Set your machine to HFAC, with the high-frequency on continuous, or use the square-wave feature if you have it, and adjust
the post-flow for 1/8-inch electrodes. Use a clean 1/8-inch electrode (pure tungsten) with the tip shaped for aluminum (not a needle-sharp point), and adjust the
flow meter for the argon to 17-20 cubic feet per hour. Set an 1/8-inch-thick aluminum plate that has been cleaned thoroughly down on the welding table. Aluminum tends to age-harden when it is exposed to air, and aluminum oxides will
constantly build up on the surface; such oxides are not always visible. Parts to be
welded need to be cleaned just before welding to provide the freshest surface.
Do not use chemical cleaners for preparing aluminum, unless it is something you
have purchased at a legitimate welding supply store. Household or automotive
cleaners may contain chemicals that will vaporize during welding and create
toxic fumes. Use a stainless-steel wire brush (not steel wool) only, and never use
this stainless-steel brush for cleaning plain steel. Since most sandpapers are
made from aluminum oxide, and this is exactly the material we are trying to eliminate when cleaning aluminum for heli-arc welding, don't use ordinary sandpapers to pre-clean.
Use an aluminum welding rod, and clean the welding rods before starting,
using alcohol and a lint-free cloth to wipe them down. The aluminum part you are
welding should be well grounded to your table. If it is lightweight plate, put a
heavy weight on part of it to keep it in contact with your grounded table, or attach
the work clamp directly to the part. Otherwise, you may find that the bottom of an
aluminum part you have welded on your table will have arc burns from intermittent contact with the table. Draw a bead on the aluminum for a short distance,
then immediately cut off the arc. Examine this weld and you will probably see
that where you stopped there's a small depression at the end of the bead. To
avoid this at the end of every weld, don't back off suddenly, but rather ease out
of it while slowly moving the tip back over the end puddle, and it should keep
from sinking.
Try to maintain a puddle of molten aluminum about 3/8-inch wide. Going too
fast will keep it narrower, and vice-versa. You won't see any real changes in the
aluminum in the way you are used to seeing steel alter during welding. The only
clue that an area has become molten is that it gets very shiny in that spot. You'll
have to watch for this change in reflectivity when making a series of puddles that
make up a bead, because aluminum melts at 1250°F, much lower than steel and
can be overheated easily with the intensity of an arc. When
welding steel, you have a whole range of colors that the
metal turns at different temperatures. These colors make it
easier to tell when you have the metal molten and when it is
just starting to cool off. You won't have this advantage with
aluminum, and you'll probably burn through a number of
samples before you learn temperature control on this metal
(see illustration).
After the weld is completed and cooled, you'll see your
bead is nice and shiny because all of the bead material has
been melted and it looks as good as virgin aluminum just
out of the foundry, but along each side of the bead you'll
see a light-colored band that is contrastingly dull. This is an
area where aluminum oxides have been vaporized from the
weld bead by the high frequency in the arc and deposited
next to the weld. If the aluminum plate you have been practicing on was not entirely clean, you may see some black
6.33 When you are learning TIG welding on aluminum, keep
spots, black "smoke" residue, or a wide dull area on either
your torch angle so that you can get a good, close look at
side of the weld bead, indicating too much aluminum oxide
how the puddle develops and the molten area becomes shiny.
was present. Inspect your welds for uniformity, appearance
You need enough heat to form the puddle, but not much more
and cleanliness, and check the backside of your welds for
or the aluminum vaporizes.
evidence of sufficient penetration.

6-14

TIG welding

6.34 When welding thick aluminum materials, or aluminum
castings like this fancy mailbox post, the edges must be
thoroughly cleaned and beveled before welding.

6.35 The rosebud tip on an oxy-acetylene torch is the easiest
method for preheating thick and cast aluminum before heli-arc
welding. In order not to warp cast-aluminum heads, manifolds
and blocks, use heat-markers on the metal while preheating.

When TIG welding any aluminum thicker than 1/8-inch, it is desirable to preheat the aluminum to 350°F before welding (see illustration). This is also particularly important when welding aluminum castings such as repairing cylinder
heads, water pumps, aluminum engine blocks, bellhousings and other automotive castings. If the casting isn't preheated before welding, it will probably crack again later on, due to the welding section being expanded
more than the adjacent metal, and then shrinking. Aluminum castings
soak up a lot of heat, so the initial welding is made easier if the part is
preheated because the part doesn't draw off the heat you're putting in
to make the seam melt (see illustration). Preheating on automotive
castings also helps bake out any dirt or oils that may be present, although any aluminum castings should be thoroughly cleaned before
even attempting to weld them. Even starting with a clean casting and a
Veed-out crack, impurities in the casting may keep coming out while you
weld.
Ideally, aluminum parts should be evenly heated in a temperaturecontrolled oven, but some parts won't fit in a regular oven, and perhaps
the boss of the kitchen may not allow it anyway. The alternative is to use
temperature-sensitive paint sticks from the welding supply. Use one
made for 350°F and dab some on various parts of the casting. Heat the
whole part with a rosebud tip on an oxy-acetylene torch just until all the
temperature indicators have melted (see illustration).
TIG-welding stainless steel should prove to be very similar to your
practice on mild steel. What makes stainless steel different from ordinary steel is its content of both chromium and nickel, part of the reason
for its much higher expense. You will find some characteristics that are
different, such as the heat staying in the bead area longer than in plain
steel because stainless steel is only about half as conductive of heat as
regular steel. Once stainless steel does take on heat, it expands some
50% more than mild steel, which can cause problems of warpage in
6.36 Weldor Bill Maguire is TIG-welding the
thinner materials if the pieces aren't clamped or jigged securely during
heated
mailbox post, using his rotating welding
the welding process. In critical welding in industry, jigs may be made of
stand he invented. At the bottom is a round disc
copper because its conductivity helps to carry heat out of the stainless
you can spin with your foot, leaving your hands
parts quicker.
free to continue welding, especially where you
In terms of setup, stainless steel can be TIG welded with the argon
have to go around something. These should be
flow set only slightly more than for steel, from 11-13 CFH for thicknesses
available for sale at the time of printing.

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Haynes Welding Manual

6.37 No one knows better what a weldor would need than a
weldor. Another invention of Bill Maguire's is this "PocketFeeder", which is patented and for sale through major
suppliers. It hand-feeds a welding wire, from .020-in. to 3/32in., to your weld, while your hand stays the same, comfortable
distance from the work. Your thumb on the wheel determines
the feed speed.

6.38 In use, the Pocket-Feeder can be used with either left or
right hands, and you can reload new wire with one hand.
Sensitivity on the thumbwheel is good, even with a light
glove on.

up to 1/4-inch. Set your current controls for DCSP as you would for steel, with
high-frequency for starting only, unless you are working on very thin pieces, in
which case you might use HFAC instead because of its lower heat input and
lesser tendency to burn through thin material. When using DCSP, the 2%-thoriated tungstens work best, with the pure tungstens good for HFAC on thin material. Of course the welding rods must be stainless steel. Practice on some stainless scraps until you get the hang of handling the different heat-transfer
capabilities of stainless. Your puddling and rod-dipping action will be at a different pace than for mild steel.
In industry, critical welds on stainless steel are often made with a setup on
the backside of the part to exclude air from the weld area. Of course, the shielding gas on top from the torch takes care there, but on the backside the weld can
be contaminated. The pros form a box or shield around the back of the weld area
and plumb some extra argon shielding gas in one end and out the other end into
a tube to carry it away from the weldor. This will purge any air from the backside
of the weld where it could cause any molten stainless-steel to crystallize. This
technique is also used in protecting the back of titanium when TIG welding.
When they weld critical tubing and can't get at the inside with a shield, they plug
each end of the tube or pipe with tape and cardboard and fill the pipe with shielding gas. This is particularly true when welding stainless-steel tubing meant to
carry medical ingredients or anything else that must be kept from contamination
or oxidation.
Although you will likely never encounter other metals in your home/shop use,
there are a variety of special alloys and rarely-used metals that are used often in
specialized industries, and for which TIG is the primary or only method found to
do the job properly. For instance, in the food-service and canning/bottling industry, there are numerous products that are transported through tubing or pipe. Besides stainless steel, nickel is often used in these applications, for its resistance
to alkalines and acids. For the same reasons, it is used extensively in the chemical industry. But nickel-alloy pipe used in these situations cannot tolerate the
possibility of a particle of slag, such as from stick welding or MIG welding, becoming included in the weld bead. It would become a weak point when faced
with continued chemical attack if high temperatures are involved, until surrounding material is affected and the joint is weakened. For this reason, nickel work
must be thoroughly cleaned before welding without using chemical cleaners, or a
black nickel oxide coating can form.

6-16

TIG welding
6.39 TIG welding is especially helpful
in situations like this race-car
suspension upright, where you have
thin chrome-moly plate and tubing,
and need total heat control. If you burn
through on a job like this, the whole
part may have to be scrapped.

For metals like nickel, copper, titanium, and others, TIG welding has proven
itself to be the most adaptable method, especially in critical applications. Since
there is no flux of any kind used in TIG welding, there is no chance of even
minute slag particles being included in the weld bead. Industry is also capitalizing
on the fine-grain structure of TIG welded seams (and the heat-affected areas
nearest the weld). Helium is most often used as a shielding gas on nickel for its
hotter arc, which allows for a higher welding speed, with a gas flow of 8-30 CFH,
depending on work thickness. Polarity is usually set at DCSP (except for thin
work where HFAC can be used to prevent burn-through), and the high frequency
control set for start-only, using thoriated tungstens. Filler rods must be nickel or
nickel alloy. Oxidation can be kept to a minimum by keeping the filler rod at a low
angle to the work and keeping the rod tip in the shielding-gas envelope.
It isn't done often, but TIG welding can be used to repair cast iron. Your
welding supply store will have some special rods that are cast of gray iron, called
"three-in-one," and these should work for either gas or TIG welding although the
same preheating instruction apply as above when we discussed welding cast
aluminum parts.
Heli-arc or TIG welding is likely to remain as mostly a shop-only process due
to the expense of the equipment and the length of the learning curve, but don't
discount it as something you can't try. If you know someone in a shop with TIG
equipment, ask them if you can spend a few hours closely observing them (with a
suitable spare helmet on, of course) performing TIG welds. The lack of spatter
and smoke from TIG welding means you can observe this process better than
most other welding methods, and this will tell you much more about how the
process works than a chapter in a book. If you feel you have observed enough to
get a good idea, see if they will let you try it out, but first offer to pay for any tungstens you ruin in your practice. You may find you have a hidden aptitude in handeye coordination, and TIG may be a process that appeals to you.

6.40 Beautiful, precise welds on
this race-car exhaust system typify
experienced, professional
TIG welding.

6-17

Haynes Welding Manual
Notes

6-18

Plasma
cutting/welding
Just as the emergence of lower-cost, higher-efficiency MIG machines has
made something of a revolution in small shop and home/shop welding in the last
ten years, so has plasma technology changed the face of metal cutting. While the
technology has been around for a while, it has been seen by most weldors as a
high-technology setup that seemed complicated or hard to use. Plasma technology's biggest usage had been in plasma arc welding, or PAW, and it is still used
in this form in many industrial applications.
The simpler plasma-arc cutting (or PAC) technology got very little play at the
time, and it has taken some years for the equipment to filter down to the general
welding/cutting marketplace. As with the MIG welders, what
was originally considered to be a professionals-only setup has
entered the province of the small shop and the amateur fabricator, due mainly to the introduction of less-expensive imported
equipment that really opened up new markets with hobbyists.
The domestic welding manufacturers suddenly became aware
of these newer markets for smaller versions of equipment they
had been selling to industry all along and brought increasing
competition to the fray. Today there's a wide selection of
plasma machines to choose from, from small 110V AC portables to large shop equipment for materials up to one inch thick.

7.1 Plasma cutting can be done outdoors, being very
little bothered by wind, makes very clean cuts on ferrous
and non-ferrous materials, and produces no smoke and
very little sparks. It has become the modern way to cut
metal. The operator here should be wearing gloves and a
long-sleeved shirt.
7.2 This illustration shows the basic components of the
plasma-arc layout. The two bottles of shielding gas are
really only required on the large industrial machines, not
the home/shop portables which run on compressed air.
The medium and larger sized plasma cutters can be used
with a straight (mechanized) torch body for trace cutting.

7-1

Haynes Welding Manual
Usage today is increasingly with the cutting side of plasma technology. With
an incredibly easy learning curve and not a lot of special installation costs, the
benefits of plasma-arc cutting, usually just called plasma cutting, are being
reaped today by body shops, muffler shops, wrecking yards, sheet-metal shops,
duct repairmen, street rodders, race-car builders and fabrication shops. Among
the benefits are use of plain shop air-compressor air, no dangerous gasses, no
flames, smoother cuts, less heat distortion in the edges you cut, little oxidation of
the edges and incredible speed.
In basic principle, the plasma process uses a torch something like a TIG
torch, but the electrode is deeply recessed up into the torch, where it cannot
contact the work and be contaminated, and the arc is maintained as a needlelike point when the air between the electrode and the work is ionized. The air or
gasses around the electrode are heated to such a point that they reach the
plasma state, in which the gasses themselves can conduct electricity. While the
gas is ionized and making continuity for the arc process between the electrode
and the work, another gas is introduced around the nozzle. In the case of plasma
welding, the gas is an inert shielding gas; in the case of plasma cutting, it is compressed air. In either case, welding or cutting, the action takes place in a very
narrow stream.

Plasma-Arc welding

7.3 In the needle-arc version of
plasma welding, the narrow-and-tall
arc forms a weld that makes 100%
penetration, top and bottom. The
technique is used mostly in precision
industrial applications.

7-2

The original plasma technology was developed in the laboratories of the
Linde Air Products Company (a pioneer in many welding processes, now the LTEC Company) back in the late Fifties. They and other companies have worked
on refining the equipment and the process ever since. You won't find plasma
welding equipment at most welding supply stores, but it is in a few industry catalogs. This is the kind of equipment usually sold through a company representative. Most of this equipment is used in high-precision joining of very thin materials. Although, up until the last ten years, both plasma welding and cutting have
been virtually reserved for industrial purposes only, and most of the plasma-arc
welding equipment is still expensive and for limited industrial usage, the process
is worth looking at.
In operation, the plasma torch has a central tungsten electrode tucked up inside a nozzle that is more restrictive than other welding gun nozzles, that is
closer to the electrode and increasingly tighter as it gets close to the tip of the
electrode, until there is just a hole for the arc to come through (see illustration).
An "orifice" gas is forced through this nozzle, and it speeds up like air/fuel mix
going through a carburetor's venturi. The gas is usually argon.
Inside the welder's power source is a high-frequency arc-starting system not
unlike a conventional TIG machine, and this initiates the arc, since the electrode
doesn't stick out and can get close enough to the work metal to start the arc itself. This is called the "pilot-arc" circuitry, and it generally cuts out after the arc is
established. The current in the electrode superheats the argon until the gas itself
conducts electricity, and a long, extremely hot arc is created that welds the work.
A second inert gas is introduced in a large nozzle around the inner one, such that
a cone of shielding and cooling gas is formed around the long arc column to protect the weld area from contamination, much as in other electric arc-welding
processes.
There are several methods of welding with plasma technology, a conventional method akin to TIG welding where filler rod is added, a needle-arc process
where parts are fused without filler rod, and a keyhole method where a weld without filler rod can be made that actually fuses the parent metal on the whole mating surface at the same time, top and bottom. The latter produces as pure and
uncontaminated a joint as possible. The benefits of using plasma-arc welding
over conventional TIG welding is that it is easier to operate as far as maintaining
the arc length exactly and the weldor has a better view of the process.

Plasma cutting/welding
Although you may find one or two PAW units in a catalog, most of the technology is used in industrial situations with mechanized torches and water cooling
with amp ranges up to 300 or 400. Most manual-operation plasma welders do
not have as much amperage as conventional welders; L-TEC's catalog shows a
110V 15-amp unit, and a 100-amp 220V three-phase machine weighing some
730 pounds that only welds up to 1/8-inch plate, although it has a 100% duty cycle at maximum output.
For those reasons, the plasma-arc welding process is probably not for your
home/shop. Much more flexible, lighter and more affordable conventional equipment is available for making welds. However, there is no question but that the
practical application of the technology in everyday situations is eminently provided by plasma-arc cutting equipment.

Plasma-Arc cutting
In plasma-arc cutting, the technology is much the same as welding, but the
arc is even more constricted, with the plasma temperature so high that the arc
7.4 In plasma-arc cutting, there is
can cut any metal. The very restricted arc cuts a pencil-thin line through the
usually only one gas (in all but the
metal, and a sharp force of gas through the nozzle blows the melted metal from
biggest machines), and that is air from
the kerf (see illustration). The velocity and steadiness of the cutting action is
the shop's air compressor, which is
such that the edges of the cuts are kept very straight and clean.
forced around the electrode to blow
The benefits of plasma-arc technology in cutting metal are many. The cuts
the kerf out neatly.
are very clean, with little oxidation of the metal as found in oxy-acetylene cutting,
the velocity of the action creates smoother edges that need a
great deal less cleanup, and in fact, with the industrial units that
are mechanized much like a gas flame-cutter or pattern-cutter,
the cuts need no cleanup or preparation for welding (see illustration). There is little or no slag found on the bottom edge of the
kerf.
Plasma-arc cutting is considered much safer in many work
environments than gas cutting. There are no flammable gasses
involved, there is no smoke from the cutting action to bother the
weldor, he can watch the process much more closely and there is
much less spray of sparks coming from under the cut. If you remember the little sparking toys you had as a kid, where you
pushed a plunger and a wheel went around, scraping against a
tiny flint making sparks, that is a small-scale version of what you
see when plasma cutting. This is in high contrast to gas cutting,
where there is a lot of heat generated, and blobs of molten metal
are constantly falling on the floor under the cut, creating a fire
7.5 Plasma cutters have become very popular with auto
hazard.
bodymen for the cleanliness and speed in cutting body
There is some heating action in plasma cutting, but in a short
panels. These sheet-metal edges need very little prep,
time, depending on the thickness of the material you have cut,
and a plasma cutter can cut painted or rusty metal just
the parts are ready to be handled for further work. With a gas
as easily.
cutting torch, the parts are still red-hot. Some have described the
plasma process as almost "cold cutting." Another benefit of the
cooler cutting action is that much less heat is induced into the parent metal, so
when working on thin materials there is greatly reduced warpage.
This is what has made the plasma cutter so popular with automotive bodymen and sheet-metal workers. Thin materials can be cut with virtually no distortion. The cuts can be made, as one bodyman described it, "as fast as you could
draw a line with a pencil." A few minutes with a file or sandpaper and the edges
are ready for some other work, whether to be welded or left as a finished edge.
Because of the lower heat and reduced sparks, panel-cutting on cars is much
easier, even if there is a secondary panel on the other side because there is less
damage to what's on the other side like other painted surfaces that need to be
left untouched. Bodymen also like the fact that you can make a cut, lay down the
7-3

Haynes Welding Manual
torch, do something and pick up the torch again and start cutting with no other
functions to perform other than putting your safety helmet down and pulling the
torch trigger. With a gas cutting torch, there is always the danger of what to do
between cuts with a torch flaming full-bore. If you keep shutting it off each time,
you have to go through the process of re-lighting and adjusting it every time.
The last reason is why plasma-arc cutting has become the tool of choice
now in wrecking yards across the country. In a yard full of discarded cars with
flammables like upholstery still in them and various pools of oil, gasoline and
other fluids soaked into the ground all around, oxy-acetylene cutting on cars in
wrecking yards has always been a hazardous job. Also, the torches and bottles
are a heavy setup and had to be hauled around to various parts of the wrecking
yard. With a good plasma machine, the 220V cutter can be plugged in a small
shed central to the yard, while a plasma torch cable as long as 234 feet could be
used to cut almost anywhere with a lot less fire danger and much faster speeds,
10 or 20 times faster than with acetylene equipment.
Because the plasma machine has arc-starting circuitry built-in, most plasma
torches do not need to contact the metal to get started, which is a decided advantage in body work. Once the arc is started and the gas is ionized and conductive, a plasma torch can cut through rusty metal, painted metal, even sections of
a car body that have Bondo or undercoating on them. When using an oxy-acetylene torch to cut painted sheet metal, the cut edges are blackened, scarred and
blistered, while with plasma the edges have a gray discoloration near the edge
and that's it.
In fabricating shops, one of the biggest advantages of plasma-arc cutting
equipment is the fact that all metals can be handled equally, from steel to aluminum, to stainless and plated or galvanized metals. It is the nonferrous metals
like aluminum and austenitic stainless steel, which are normally hard to cut
cleanly with other methods, that make the plasma machines appealing to shops.
The author remembers his first experience with a plasma cutter some years
back. An aluminum motor plate was being made for a race car, and we needed
to cut a 14-inch hole out of the center to clear the flywheel. The material was 1/4inch-thick aluminum and 7075-T6, which is so hard you can have difficulty even
drilling it unless you have a fresh bit. The idea of using a sabre saw or band saw
seemed tedious and out of the question. We took it to a shop that had a plasma
cutter and within minutes of making a plywood circle template to run the torch
around, we had our hole cut with very little heat and perfect
edges. It was eye-opening, and when you try one you may be
similarly amazed.
When plasma-arc cutting equipment first came into
wider, less-industrial usage, some traditional fabricators and
bodymen were intimidated. The technology wasn't widely
understood, and the term "plasma" seemed to indicate some
highly-technical process akin to esoteric lasers. Once the
machines got out into the field, they quickly became accepted for their speed, cleanliness, lack of maintenance,
lower fire hazards and the ease with which a weldor can operate them. It's almost a pull-the-trigger-point-and-shoot
kind of process.
Perhaps one of the bigger attractions of plasma cutting
equipment we haven't mentioned yet is the type of gasses
used in the process. While the big industrial plasma machines do use traditional shielding gasses, like argon for the
arc "pilot" gas and hydrogen, nitrogen or a gas mixture (like
35% hydrogen/65% argon) as the cutting gas, most portable
plasma units today use nothing more than compressed air
7.6 Shop air-compressor air is all that's required to run most
plasma cutters. Here on the back of a Thermal Dynamics
from a shop air compressor (see illustration). There are no
machine is the air filter and pressure regulator.
expensive bottles to buy or periodically refill.
This is how the shop-air works. When the gas in the arc
7-4

Plasma cutting/welding
column is ionized, it becomes the arc medium between the work and the electrode. Nitrogen happens to ionize well and makes for a hot arc, and also happens
to make up about 75% of the air around us by weight. Most plasma cutters use a
high velocity of shop compressed air to become the ionized arc gas, the cutting
gas that blows the material out of the cut, and the cooling medium. It can be assumed that all shops already have a heavy-duty air compressor on hand for operating other equipment, so using shop air greatly simplifies the use of a plasma
cutter and keeps expenses down. In industrial situations, pure nitrogen or hydrogen or a mix is used for totally clean cuts in precision work, but the shop-air cuts
are more than good enough for any automotive or fabricating-shop usage.

Choosing plasma cutting
equipment
The large, expensive and heavy industrial plasma cutters and welders are for
specific purposes in high-precision and high-production mechanized work, often
requiring two gas bottles, three-phase power for 200-600 amps, and use water
cooling for the torch as well. For these reasons, we'll concentrate on the wide array of more portable plasma cutters that are available for home and shop use,
most of which operate on 220V, single-phase current and use only shop compressed air for cutting and cooling.
At the most basic level, where a home/shop user might be interested, there's
a number of domestic and imported plasma cutters that weigh 75 pounds or less
and are capable of cutting material thicknesses that an automotive user would
come across. If you are comparing plasma cutters to welders, don't be alarmed
at the amperages on the smaller plasma machines. Units with 50-amp capability
can cut steel up to 3/4-inch thick. An area where there is a comparison with
welders is that smaller plasma machines have lower duty-cycles and their cutting
speed slows down when thicker materials are cut.
In the 110V category, Daytona Mig offers the Pocket Plasma , which
puts out 25 amps at a 20% duty-cycle and cuts sheet metal at 100 inches
per minute, though it is said to cut up to 3/16-inch steel material. It requires
70psi air input at a rate of 4-6 cubic feet per minute (cfm). Miller makes several 110V units, with the Spectrum 187D cutting up to 9/64-inch steel material and weighing 47
pounds. Thermal Dynamics
starts their extensive line off
with the DynaPak 110,
which cuts up to 3/16-inch
steel, uses all solid-state
circuitry, sequential status
lights, and has an amazing
80% duty-cycle at 20 amps
(see illustrations). With all
of the machines available,
the maximum cutting thickness is usually given for
mild steel, while aluminum
and other non-ferrous material take more amps and
the same machine can only
cut a lesser thickness of
7.7 The compact end of the plasma cutter
7.8 Another quite-portable plasma machine
these metals. On some mamarket is represented by 110V machines
is the PCM-VPi from L-TEC, which offers cuts
chines, a figure may be adsuch as this Plasma Pocket from Daytona
up to 5/8-inch in steel, variable amps from 10MIG. It puts out 25 amps, weighs 55 pounds,
vertised that gives a maxi40, and a 60% duty-cycle at its rated
and requires 4-6 cfm of air at 70 psi.
mum thickness for cutting
maximum. It operates on 220V current.
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Haynes Welding Manual

7.9 One of Miller's smallest plasma cutters, the Spectrum 187D
weighs only 47 pounds, yet cuts up to 9/64-inch materials, and
runs on 110V house current.

7.10 The popularity of plasma-arc equipment has really
jumped in the last five years. Now imported units are sold
here, and tool companies like Matco have them, as well
as the traditional welding equipment manufacturers.

7.11 HTP's entry-level plasma cutter takes 220V current, but
weighs only 56 pounds and is said to cut up to 1/4-inch steel. It
has a 100% copper-wound transformer.

7-6

and another, higher figure for severing. The severing
action is a short cut, such as when cutting a length of
material.
Beyond the 25-amp range that seems to be the
limit for 110V equipment, there are machines for 220V
input that are still quite portable. HTP America offers
affordable plasma cutters from their Micro-Cut 250 that
cuts up to 3/16-inch steel, to the Micro-Cut 375 which
can be used on 110V, 220V or 460V input and offers
7.5-35 amps, cutting up to 3/8-inch steel, as well as
larger shop units (see illustration). L-TEC has a popular unit, the PCM-VPi, which weighs only 46 pounds
with its plastic case and carrying handle, but is said to
cut up to 5/8-inch steel with its 50 amps of power, and
features a 60% duty-cycle at 40 amps output (see illustration). It is a good choice for any automotive
shop, and can sever up to 3/4-inch material such as rebar for construction sites. Lincoln's entry-level plasma
cutter is the Pro-Cut 40, with a 60% duty-cycle at 40
amps, 220V input, cuts up to 3/8-inch steel, and offers
a timed pilot arc and timed post-flow. Daytona MIG's
medium-sized lineup includes a 35-amp, 220V Plasma
Prof 35 that is said to cut up to 3/8 steel quickly, and
1/2-inch steel at 15 inches per minute.

Plasma cutting/welding
Above the 50-amp range, plasma-arc cutting equipment is in the
serious shop equipment arena. Most of these machines are for 220V,
three-phase power input, which you won't have at most home
garages or small shops. Within this large group of choices though,
there are cutters with total amperage ranging from 50 amps to 150
amps or more. In this category, you'll find the Lincoln Pro-Cut 125,
with 125 amps, 60% duty-cycle, a microprocessor-controlled overshoot limiter, and "Drag-Detect" circuitry that is said to prevent consumable damage. In this machine, let's look at the duty cycles for a
professional-grade plasma cutter. Rated at 60% duty-cycle at its
highest 125-amp output, it has an 80% duty-cycle at 110 amps, and
a 100% duty-cycle at 100 amps or less. At its highest output, this
machine can cut 1 1/4-inch steel, and for ordinary 1/2-inch plate, it
can cut all day long. That's the difference in the heavier professional
machines; they have stronger components to work heavy materials
not just a few times a day, but all day, which is why they are overbuilt
and too expensive for the home/shop market, even disregarding the
three-phase input power required.
Other powerful plasma-arc cutters include: HTP's PCA 65, with
60 amps (220V single-phase), cuts up to 3/4-inch steel (clean cuts on
5/8-inch steel), a 50% duty-cycle at 60 amps, and a weight of 180
pounds. HyperTherm has their 100-amp MAX 100, that will cut 1 1/4inch steel on 220V or 440V three-phase power, with CC (constantcurrent) transistorized output, ESAB offers the PCS-90
that cuts up to one-inch steel
with three-phase 220V or
440V, and has air pre-flow,
post-flow and a low-air-pressure sensor. L-TEC has the
PCM-1000i, which can cut
one-inch steel at production
speeds with its 80 amps, and
a 70% duty cycle at that
maximum amperage, yet
weighs only 80 pounds. Daytona MIG has a full line of
heavy-duty plasma cutters,
with the Plasma Prof 120 being near the top with 120
amps (220V three-phase),
cuts up to 1 1/8-inch steel
and 7/8-inch aluminum, with
7.13 Still light and portable, but
quick-disconnect torches so
powerful enough to cut 3/4-inch
you can switch to a mechansteel, The L-TEC PCM-750i has 50
ical torch for a cutting table
amps
with a 40% duty-cycle at that
(see illustrations).
setting, and has its own torch
Most of these machines
storage spool and spare parts
offer such features as infistorage compartment.
nitely-variable output control, which means that you
7.14 The larger plasma-arc cutting
can dial in the exact requiremachines are all in the three-phase
ments for a job, say cutting
power category, like this Plasma Prof
through an outer skin on a
150 from Daytona MIG. It weighs 317
pounds, has a range from 20-150
vehicle without cutting panamps, and can cut 1 1/2-inch steel
els on the other side. Of
and 1-inch aluminum at 30 inches
course, you can cut thin maper minute.
terials with more power than

7.12 The bigger-amperage machines are all in the
220V category, and many, like this Daytona MIG
Plasma Prof 50, require shop-type three-phase
current, too. This one has a 35% duty-cycle at its
rated max of 50 amps and 100% at 30 amps.

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Haynes Welding Manual
is required, but using just the right amount means you have the
least danger from flying sparks. On the less-expensive end of the
plasma cutter spectrum, some of the machines offer only a knob
with several predetermined positions.
Beyond the 80-120 amp range of plasma cutters, where really large plates are cut all day long, the equipment offered is no
longer usable with shop air, requiring two inert gas supplies and
water-cooling for the torch. However, they offer from 100 amps to
as much as 600 amps (the higher amperages are usually found on
machines built to be used with mechanized torches), and all with
100% duty-cycle. Obviously, that kind of power doesn't arrive at
your doorstep without a hefty invoice.

Using a plasma cutter
If you thought the modern MIG welder brought great advancements in ease of the learning and operating curves, wait until
you try plasma-arc cutting. It's as much of an improvement over
gas-torch cutting, in both learning curve and reduced mainte7.15 Larger machines are usually offered with an
nance. We watched as a race-car mechanic in a large shop was
optional 180-degree (straight) torch for use with
being trained by another worker to utilize their plasma cutter. The
shape-cutting machines for industrial work.
newcomer to the technology made his first 4-inch by 6-inch part
from 3/8-inch steel plate after only fifteen minutes of instruction.
After experimenting with different speeds, power levels and materials, he was ready to do real jobs after an hour. You can't learn everything there
is to know about the process in your first day, but this story is typical of first-time
users.
Unlike welders, most plasma cutters of the shop-type variety are ready to
use when you uncrate them. Their power cord is ready to plug in (you don't have
to put on your own plug), the torch is usually already hooked up to the front of
the machine, and all you have to do is connect your shop air supply before making your first cuts.
Although the risk of fire or injury is less with a plasma cutter than with a
welder or oxy-acetylene cutting torch, you must still take every precaution before
starting. Read over the instruction manual that came with your machine before
doing anything. When you are familiar with all the controls, take the torch apart,
so you'll understand how it works. Specific design of electrodes and other parts
may vary from make to make, but, whatever the make,
you'll notice that the electrode is like no other you've seen.
Instead of a six-inch-long rod of tungsten as with a TIG
torch, the plasma electrode is a machined part.
Although it never comes in contact with the work, the
plasma cutter's electrode should still be considered a
"semi-consumable" item. Electrodes can last a long time,
but keep several spares on hand because they do get worn
and contaminated with material blown back from the cutting (see illustration). Besides the electrode, you'll find
several other pieces inside the plasma torch, including the
nozzle (also called a shield cup, retaining cup, and gas diffuser), and a cutting tip, which is what converges the airflow
past the electrode (see illustration). Different brands of
torch may have small springs, insulators or swirl rings, but
the basic principle is the same for all brands.
There is much less danger with a plasma cutter than
7.16 Eventually, enough material will blow back from cutting
other
equipment, yet there are still hot sparks generated.
to cause a building of slag on the exposed nozzle and orifice
There is also ultraviolet radiation. Because the process
of the torch, requiring periodic maintenance.
doesn't seem as bright or intense as welding, some users
7-8

Plasma cutting/welding

7.17 The main components of a typical plasma-arc cutting
torch are, from left: torch body with o-ringed and threaded
extension, the swirl ring, the electrode, the cutting nozzle, and
the retaining cup. Some brands have a slightly different
arrangement of parts inside.

are tempted to perform plasma cutting without proper safety wear, but your skin
can still be burned. So wear long-sleeved shirts with the collar and cuffs buttoned up, and wear leather welding gloves and a full-face shield. If you ever have
to work on your machine, it should be unplugged, even if all you are doing is
changing the electrode. The machine's output is high enough voltage to cause
severe shock and injury. Also, if you are cutting any painted, plated or galvanized
metals, ensure that you have adequate ventilation. The plasma process doesn't
create fumes by itself, but what's on the surface of the metal can.
On most machines, there is a high frequency arc-starting circuit that makes it
unnecessary to touch the work with the torch to initiate the arc. Set your output
voltage at the machine, depending on the thickness of the metal you are cutting.
On some of the smallest machines, there may just be an on/off switch, or a
switch with two or three amperage positions. Most machines have a variable
knob spanning from the machine's minimum amperage to its maximum.
Use a guide of some kind to make straight practice cuts (see illustration).
Place the torch so that the outer cup rides on your guide with the nozzle the suggested distance from the work and just push the button. The arc will start, it will

7.19 You'll need to keep on hand some spares of each of the
torch components, including wrenches for changing the tip
and the electrode.

7.18 Hot rodders never leave anything
alone. Rugged Thermal Dynamics 50amp plasma cutter used in a rod shop
has been modified with the addition of
a tubing rack and box on top to hold
nozzle dip and plasma consumables.

7.20 The plasma cutter makes very clean cuts, so any
raggedness on yours means your hand wasn't steady. Use a
sturdy guide whenever possible. With a piece of tubing as a
straightedge, here a dry run is being made to ensure the
torch follows the correct cut line.

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Haynes Welding Manual

7.21 This clever tool snapped onto a Miller plasma torch
holds the torch just the right distance away from the work, so
if you have this and a sturdy guide, your cuts should be
almost as good as machine-operated torches.

7.22 Same tool as the previous photo, showing how it holds
the tip away from the work, and provides a good surface to
lightly drag against your pattern or straightedge.

pierce the metal (no need to go to the edge of a plate to get the cut started) and
begin blowing the slag out the bottom. Move along at a steady speed and you're
cutting. You'll develop a feel for the correct cutting speed for various materials,
but the instructions with your machine should tell you the recommended speeds
for various thicknesses and materials. Practice moving the torch a few times
without the arc, just to see how fast or slow 15 inches per minute may be, and
what 100 inches per minute feels like.
Examine the cut edges of the material. If the lines in the cut are not straight
up and down, your speed was off (see illustration). If the lines turn to the direction the cut was made from, your cutting speed was too fast. You can also have
someone else observe you from a short distance while you are cutting. They will
tell you if the sparks went straight down (proper speed), or sprayed more to the
direction the torch came from (too fast). Moving too fast can cause premature
failure of the nozzles.
When the part you have cut is cool enough to pick up,
examine the kerf. If your cutting speed and amperage was
right, the small amount of slag at the bottom of the kerf can
be easily clipped off with wire-cutter pliers, and the rest of
the metal should take minimal cleanup.
In cutting shapes, you can use plywood patterns to cut
repeated shapes such as round or square holes or anything
else. Just make the template the right size for the torch
head to follow. For basic circles, most welding supply
shops have a circle-cutting tool (sometimes called a circlecutting "compass") that can be used with a plasma cutter.
By far the most important thing to maintaining and operating your plasma-arc cutter is the condition and quantity
of the air it runs on. Read the manufacturer's recommendations for the size of compressor you need and the pressure
and cfm requirements. If you try to make a cut when you
don't have enough air, most machines will either not start or
7.23 At top here are two cuts made with a hand-held plasma
cutter. In the top one the torch was moved too fast and with
make a grinding-like noise inside. Besides having enough
not enough amperage. The middle plate had the speed more
air, plasma cutters also require clean, dry air. Most will
correct. The bottom plate for comparison only was oxycome equipped with a drier/regulator right at the air-line
acetylene cut with a machine, so this is the smoothness you
connection on the back of the machine, but you also need a
are trying to duplicate. Only a gas torch cut would have this
good drier on your compressor. And, if your compressor is
discoloration of the metal showing.

7-10

Plasma cutting/welding

7.24 As with traditional torch cutting, soapstone is useful to
mark your cut lines because it won't burn off. With the
reduced heat of plasma, you could also use a marker pen.
Sharpen the soapstone before drawing.

7.25 Here an exhaust gasket is being traced to make thick
header flanges from a piece of 3/8-inch steel plate.

very far from where you hook up the flex line to the plasma cutter, it's a good
idea to install one on the wall just ahead of the connection for the flex line (see
illustrations). Your compressor and the driers should all be drained every night
to remove dirt and moisture. Moist air will rapidly deteriorate the electrodes and
nozzles.
Cutting too fast or trying to cut too thick a metal for the size machine you
have will cause some slag buildup inside the nozzle of a plasma cutter, not unlike the buildup inside a MIG gun. In fact, you may use the same anti-spatter
spray or dip in your plasma cutter as you use on your MIG torch to make the
slag buildup easy to remove. Eventually, even if you take care of your plasma
torch, you will have to replace nozzles and electrodes because usage will enlarge the holes, making for a less-concentrated arc. If any slag is "fried" onto the
nozzle or electrode, sand it off by holding the part squarely against sandpaper
on a flat surface, and then clean out any
orifice holes.

7.26 The 50-amp plasma cutter
makes short work of cutting out the
patterns and can easily pierce the
center of a pattern to cut out internal
holes and shapes.

7.27 Dry, clean shop air is extremely
important to extending the life of
your plasma nozzles and electrodes.
These HTP Super-Dry air driers have
a bronze filter and desiccant inside
that changes color when it needs to
be changed.

7.28 In most applications the HTP
Super-Dry disposable filter/driers
can be screwed right onto the rear
of your machine.

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Haynes Welding Manual

7.29 You can't have the air too dry for use with a plasma
cutter. If your compressor is outside or a long distance away,
use an extra filter/drier on the wall where the hard line
switches to the flexible hose for your plasma cutter.
Drain daily.

7.30 The Max-Dry from HTP is a three-stage system. Stage
one is a self-draining 5-micron filter, stage two is a
"coalescing" filter, and the final stage is another filter with a
large amount of desiccant. The desiccant changes color when
it can't absorb any more humidity, but can be dried out in an
oven for reuse.

You'll find there isn't too much to discuss further about how a plasma cutter
operates. They are at the same time technologically advanced, and yet simple to
operate and maintain. They perform exactly as they are claimed to, in terms of
speed, cleanliness of the cuts, lack of cleanup required and the minimal heat induced into the adjacent parts. Plasma-arc cutting is most definitely the preferred
modern method of cutting metals, in situations ranging from an air-conditioning
duct repairman or an automotive bodyman working on gauge metal to industrial
plants where shapes are cut from thick plates all day long. To most automotive
enthusiasts and race-car shops, the modern shop combination is a good MIG
gun for welding and a companion plasma machine for
cutting (see illustration).

7.31 Daytona MIG offers several air filters, from left: the
disposable filter element, a wall-mount filter housing,
machine-mount filter housing, and in front a small
disposable filter.
7.32 Given his preferences, today's hot rodder, race-car
builder, farmer or fabricator would like to have one of each a reliable, easy-to-use MIG welder, and a safe, clean and
equally easy-to-use plasma cutter.

7-12

Safety & shop
equipment
When it comes to equipment for working with metals, there's a lot more required than just a means of cutting metal and fusion-joining it. Many automotive
enthusiasts are "tool addicts" to begin with and welding just adds another dimension to the want list.
Other than your welding/cutting equipment itself, the two main requirements for a
good environment are the proper safety
gear, particularly the goggles or helmet, and
a clean, safe, well-designed welding work
area or table. As you'll see, there's a wide
variety of helmets available. Choose one
that you are comfortable with and that
meets your budget. You may have gotten a
basic helmet with your welding machine,
and you can use that until you save up for
one of the more advanced models. Other
personal safety equipment would include
steel-toed industrial safety shoes (available
at most shoe stores), good leather gloves,
fire-resistant long-sleeve shirts or, if you are
arc-welding, a leather welding jacket and/or
apron.
A clean, safe welding table setup is of
paramount importance. While you are learning, there will be a lot more sparks and slag
8.1 You'll find most of your welding safety gear and clothing at your local
generated than when you are advanced,
welding supply store, such as helmets, leather protective wear, gloves and
and your welding table should be heavy
safety shields or goggles.
steel, positioned well away from all stored
8-1

Haynes Welding Manual

8.2 This Hunstman welding helmet offers full face and chin
protection, and features a flip up welding lens. When you are
setting up to weld, the helmet can be down on your head and
you look through the clear lens, then flip down the dark lens
just before welding. Some weldors find these better than fixed
lenses where you have to shake your head to flip the whole
helmet down.

8.3 This L-TEC helmet from ESAB, called the Liftorama,
features a lift-up safety lens, and underneath a shatter-proof
clear lens that can be used when grinding a weld.

flammables and with a clear area underneath for any sparks
or molten slag to be safely contained without having them
scooting across the shop or lodging on top of your shoes.
For metal cutting, you need a good "grate" setup as pictured in Chapter 3. You will also need some firebricks,
which are helpful to practice welds on because the work
won't stick to them. Do not just cover your old wooden
work bench with a piece of sheet metal and call it a welding
table. Invest in a piece of plate from a scrap yard. When you
put a lot of heat into welding projects on a tin-covered
wooden surface, enough heat can go through the metal to
start the wood smoldering, perhaps even starting a fire after
you have left the shop. Also, you must have proper fire extinguishers on hand, preferably an ABC type or halon, that
can put out all kinds of fires.
Much of the work of sizing and joining metals for
home/shop projects will involve tools you already have,
such as a drill press, grinders and sanders, clamps, measuring equipment, squares and levels. A common hacksaw
8.4 Another L-TEC helmet, the Weldorama offers a clear sight
can be used to sever lengths of material but can be tedious
plate above the welding lens, so the weldor can keep the
on heavier-wall stock. Sheet metal can be cut with aircraft
helmet down, and then just shift his eyes to the dark lens
tin-snips, manual or electric nibblers, or a plasma cutter.
when he is ready to weld.
Many of the tools shown here are special-purpose
tools that you may not have already, and which perform
special functions that relate to improving welding work or
holding materials to be welded. All of them are useful when the time comes. We
all wish we could just put one of each in our home garage, but you may have to
collect them over the years as your projects get more involved.
We also show here some tools and equipment that were made by fabricators
8-2

Safety and shop equipment

8.5 The Scanorama helmet was designed for MIG and TIGwelding applications, with a large shade 5 filter disc
surrounding the welding lens. You can see most details
through this area, but your skin is still protected from
radiation. You look through the darker portion when welding.

8.6 This Darth Vaderish design from ESAB is the Autorama
2000, which one of a modern breed of welding helmet with an
automatically-darkening lens. The lens is powered by solar
cells, and turns dark as soon as the welding arc begins. These
are considered by many weldors to be much easier to use
than flipping a helmet up and down to set up each weld.

8.7 Daytona MIG offers a variety of modern safety helmets, and a special, clip-on lens (foreground)
that attaches to your MIG gun. It allows you to set up a weld, then look through the lens when making
spot-welds without the bother of a full helmet.

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Haynes Welding Manual

8.8 A good pair of leather welding gloves will last you for many years, but if you
are using oxy-acetylene equipment, keep an extra-clean pair for use with this
equipment. A spurt of oxygen on a dirty glove could cause combustion, so don't
use these good gloves for handling hot or dirty parts.

8.10 A clean, safe welding table area promotes good work. Your home
shop won't need a steel-plate table this big, but note how uncluttered
and organized things are here in a professional shop. A rack under the
table holds all the C-clamps.

8.9 From HTP is this Super Spark Guard
welding blanket. It can take up 2300° F, and
can be used when working on a car to
protect the window glass, dash or interior. It
measures 37 inches by 50 inches.

8.11 A very useful tool when welding on thin
materials such as newer-car body metal is a
copper "spoon." The heat-absorbing spoon can
be used to back up butt welds or when filling
holes in sheet metal. The welds will not stick
to the copper.

and hot rodders for their own use. These are typical of projects you can do once
you have practiced your welding skills, and some represent considerable involvement, though on the part of someone who has already "been there."
Sources for the commercial products in this and other chapters can be
found in the Sourcelist at the end of this manual.

8-4

Safety and shop equipment

8.13 This welding shop has a dedicated grinder for sharpening
tungstens mounted right on the side of the TIG machine. The
rubber bungee cord kills the vibration noise when the grinder is
slowing down.

8.12 If you get into a race-car project, you might
invest in one of these tubing notchers. Available from
Eastwood, Williams Low-Buck Tools, Speedway
Motors and other sources. It fits in your drill press and
allows precise fish-mouthing of tubing via a captive
hole saw.

8.14 Eastwood offers this magnetic quick-clamp which functions to
hold parts in alignment at various angles for tack-welding.

8.15 This unique spot-welding gun for sheet-metal
work has a power lead that clamps into the electrode
holder of your arc welder. Use the trigger to make the
electrode touch the work, pull up for 5 seconds, then
pull all the way to break the arc. Get it from Eastwood.
8.16 One of the handiest shop tools we have ever
used is the Milwaukee "Porta-Band", which as the
name implies is a portable bandsaw. It cuts fast and
straight and is very helpful in cutting tubing at angles
and other chores associated with welding projects.

8-5

Haynes Welding Manual

8.18 Other kinds of metal-cutting power saws include this type, which
uses a bi-metallic toothed blade, here being used to cut clean through
aluminum tubing.

8.17 A "Radiac" or cutoff saw with an abrasive blade
is very fast and secure when cutting large amounts
of tubing. The work is held in a moveable vise so
angle-cuts can be made. This one is cleverly
mounted on a 55-gallon drum to capture all the
sparks and debris.

8.19 In auto bodywork, a tool like
this can be used in your electric drill
to cut out factory spot welds to
remove panels for replacement.

8.20 For Eastwood offers a
similar tool for removing spot
welds which features a hexsided drive end, so it can't slip
in your drill chuck.

8-6

Safety and shop equipment

8.21 W e l d o r Bill M a g u i r e m a d e u p this e l e c t r o d e r a c k
for his T I G m a c h i n e f r o m a rolling p l a t f o r m holding 15
plastic p l u m b i n g p i p e s w i t h c a p s , e a c h m a r k e d for t h e
size a n d t y p e of e l e c t r o d e . A b u n g e e c o r d holds t h e m in
t h e r a c k . T u b e s k e e p t h e r o d s c l e a n a n d dry.

8 . 2 2 Y o u n e v e r k n o w w h e n you'll find s o m e t h i n g t h a t
c o m e s i n h a n d y i n t h e s h o p . This h u g e a n d hefty r o u n d
p l a t e w a s f o u n d a t a m e t a l y a r d a n d b o u g h t a t t h e perp o u n d price. It's d e a d flat a n d c a n n o t w a r p , a n d h a s
m o u n t i n g holes in it for c l a m p i n g w o r k to it.

8.24 A disc s a n d e r w i t h at least 1/2 h o r s e p o w e r is very
h a n d y a r o u n d t h e s h o p for s q u a r i n g e d g e s o f f l a m e c u t
p a r t s , a n d t a k i n g s h a r p e d g e s a n d c o r n e r s off w o r k .
8.23 If y o u p l a n to do a n y o r n a m e n t a l iron w o r k or m a k e a lot of
b r a c k e t s , an i r o n w o r k e r like this is very h a n d y , It c a n b e n d solid
r o u n d , s q u a r e o r hex s t o c k , a s w e l l a s b e n d r o u n d t u b i n g a n d flat
s t o c k into r e p e a t a b l e s h a p e s .

8-7

Haynes Welding Manual

8.25 Ideally, you would have both a disc sander and belt sander for a
variety of metal finishing needs. There are combination units, but beware
of weak-powered sanders. When you put the rough edge of a 3/8-inch
plate up there to sand, they stall easily.

8.26 HTP is marketing this clever belt-sander
that can get deep into corners and places where
regular sanders and grinders can't reach. The
belt guide rotates 160 degrees, and the sander
uses 3/8-inch belts.

8.27 Something that is always a problem in body work when replacing
panels is getting parts aligned properly before making a butt-weld.
Eastwoods Intergrip clamps space the two parts .040-inch apart for full
penetration. After tacking the panels, you can disassemble the clamps.
8.28 Nothing beats the original Cleco clamps and pliers for testassembling sheet-metal parts. Originally developed for aircraft use, these
operate like reusable, temporary rivets. In blind holes you insert the
fastener with the pliers and the two parts are held together, but come apart
easily with the pliers again. HTP offers this set.

8-8

Safety and shop equipment

8.30 For small jobs, Eastwood offers these little Cleco-type
panel holders that you operate with your fingers. No tool is
needed. They have a range of up to 1/4-inch for thickness and
fit a 1/8-inch hole.

8.29 You can see here how the pliers extend the tip of the
Cleco fastener through a set of holes. When the tool is
released, the Cleco grips the parts. Also available are Cleco
mini-clamps (right) that exert a temporary hold while you
tack-weld small parts together.

8.31 When you want to spot-weld sheet-metal panels that
didn't have them originally, like new parts or repair panels you
have made , a manual flange punch like this is a real help.
This one is from Daytona MIG.

8.32 An air-powered "panibbler" is a fast, clean way to cut sheet metal up to 3/64-inch in steel or 5/64 in aluminum. It will follow
a pattern or cutline very closely, and you control the speed with the throttle. This one is from HTP.

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Haynes Welding Manual

8.33 The HTP stud setter is a great boon to bodymen, who
used to have to pull out creases and dents by drilling holes
and using slidehammers that distorted the metal even further.
This 110V tool saves considerable time and labor.

8.34 Small-headed copper-plated "studs" are
inserted into the magnetic head of the stud setter.

8.35 On a dented area that has been ground to clean
metal, the tool is pushed in contact with the metal and
the trigger is pulled for a half-second.

8.36 The suds are spot-welded in place, and a special
slide hammer is used to pull out the dent or crease. Studs
hold 500 pounds of pull.

8.37 On this dent, the first three studs pulled out the bulk
of the damage, and two more are in place to pull the last
bit out. Note how the first three studs have been clipped
off with cutting pliers.

8.38 After the pulling, the stud heads are easily ground
off without distorting the metal, and there are no holes
left to fill in, as with conventional methods.

8-10

Safety and shop equipment

8.39 Visit most street rod shops, fabrication shops and race-car
facilities, and you'll find that a lot of the shop equipment they have is
homemade, and these are the kinds of things you'll be able to do once
you have welding and cutting equipment.

8.40 A simple steel materials rack like this is great for keeping tubing,
bar stock and flat stock out of your way, and is easily constructed. In
front of this one is an electric, automatic bandsaw great for making
unattended cuts. This one was purchased inexpensively at a tool
auction. Watch your newspapers for industrial auctions and
shop foreclosures.

8.41 An old truck rim, a length of round pipe and a
piece of scrap plate are combined with welding to
make a perfect small welding table or mount for a
grinder or sander.

8.42 Leftover pieces of tubing
and other stock should be
saved in a barrel. You never
know when you need a short
piece. This fixture for making
up a street rod four-link rod is
made from short pieces of
angle-iron and a length of
rectangular tubing.

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Haynes Welding Manual

8.43 Ideal for holding small brackets onto tubing for tacking are
these magnetic blocks, available at most welding supply stores.

8.45 Another type of angle
fixture from HTP is this type,
which clamps the two parts at
a perfect 90 degree angle for
tack-welding.

8.46 The Eastwood anti-heat is a putty-like paste that
can be formed around heat-sensitive parts when you are
welding near them. The paste absorbs heat and can be
used to protect auto glass when welding near it.

8-12

8.44 HTP and other companies offer these strong
magnetic holders that can secure two pieces of tubing
for angles of 45 degrees, 90 degrees, and 135 degrees.
Tack the parts then move the magnets to the next joint.

8.47 Daytona MIG sells this handy spot-sandblaster. It is useful
for cleaning paint and rust away from a spot your have to weld,
like a recess where a regular sander won't reach. Three-quarters
of the blasting media is returned to the gun, so it won't make your
shop a "sandpit."

Building a
utility trailer
One of the most common home/shop projects for welding equipment is a
trailer of some kind, Which can be used for carrying a race car or off-road vehicle or On a smaller scale, can function as a utility trailer. Each of these is easily
within the realm of the hobbyist, though a trailer of any size should not be your
first welding project. Hone your cutting, fitting
and welding skills on other, less critical projects
first, like a metals storage rack, a wrought-iron
front gate, a fireplace grate, barbecue grille or a
rolling cart for your welding equipment. Frankly,
the latter is usually the first welding project after
the practice sessions. Many are the accomplished weldors we have met who say they
welded up their oxy-acetylene equipment cart
some 20 years ago and are proud to be still using it.
Since the trailer project is something to be
used on public roads and at highway speeds,
you want your welding quality to be good before you get started because the welds here
have to be strong, not just good-looking. The
basic construction details of any trailer are fairly
similar, whatever the size. You assemble a rectangle of steel tubing or angle-iron, attach a sus9.1 A 4x8-foot utility trailer like this is a good project
once you have perfected your welding and fitting
techniques. Once you have a trailer like this, you'll
wonder how you ever got along without one. It can be
used for hauling camping gear, lumber, yard trimmings,
a go-kart or furniture.
9.2 Find a good trailer supply store in your area, where
you can browse for suspension parts, wiring, lights and
hitch components.

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Haynes Welding Manual
pension and axle system, add a floor and
sides, taillights, safety chain and a hitch in
the front. Most smaller trailers, from 4x8foot size and down, can be constructed of
2x2 tubing, or 2x2 angle-iron, depending on
the hauling requirements. A trailer such as
we are illustrating here is capable of carrying motorcycles, a go-kart, personal watercraft, garden tractor, camping equipment,
building materials, firewood or landscaping
dirt. With a few simple poles and some canvas, you could actually use it to camp in,
like a homemade pop-up camper. We built
this one of 2x3 tubing and 2x2 tubing of
1/8-inch wall thickness, which is somewhat
overbuilt, but these were the materials that
were accessible, and the cost of building
such a trailer is entirely dependent on your
materials. If you were building a car-hauling
trailer, you would use two axles, preferably
9.3 We purchased this Chevrolet Sprint solid rear axle and springs at a do-itwith brakes, and use diamond-plate steel
yourself wrecking yard very inexpensively. New trailer axles and springs can
for the floor, with some very sturdy ramps.
be expensive, but you can often find used ones at swap meets, or you can buy
an old, small boat trailer that you can rework into a utility trailer.
If you can get much of the steel from
the scrap or remnant pile at your local metal
source, scrounge used plywood or surplus
diamond-plate steel and get your axle and suspension from a donor car at a
wrecking yard, such a trailer can be built for 1/3 to 1/2 the cost of a newly purchased trailer of the same size. You'll need some kind of metal cutting equipment
beyond the basic hacksaw or your arm is going to get tired. There's a lot of metal
to cut to build even a simple trailer. You could lay out your plan on the driveway
or garage floor, mark all your materials and bring them to a shop for cutting if you
have to, then bring them back home to weld. Welding such a project can be done
with any of the equipment we have discussed in this
book, but it goes together fairly quickly with either arcwelding or MIG-welding.
We used inexpensive-grade plywood for our
trailer sides, which we made two feet high, and a better
grade of 3/4-inch plywood for the floor bolted to the
frame with carriage bolts so the floor would remain
smooth enough for easy rolling of a furniture dolly into
the trailer. Once you have built such a trailer, it's like
having a new truck. Everyone you know will want to

9.4 Bolt your springs, U-bolts, spring plates and shackles
together, making sure the springs are square to the axle centerline
and measuring the same distance apart front and rear.
9.5 Attach a hitch to the ball on your tow vehicle, and mock up the
assembly, using 2x4s to simulate the rails. This should give you an
idea of what size and layout of trailer you want, and where to
locate the axle and wheels. Keep more trailer frame in front of the
axle than behind, to insure you have enough tongue weight.

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Building a utility trailer

9.6 In our case, we determined that the Sprint axle was too narrow for our
purposes, since we wanted a full 4x8-foot sheet of plywood as a floor. This
meant widening our tubular axle 7 inches.

borrow it to move something. Our tailgate was made from a
frame of one-inch-square steel tubing, .063-inch-wall, and
we tack-welded to it a section of steel mesh such as is
used for barbecue grilles. The hinged tailgate allows wind
to flow through the tailgate on the road, reducing fuel consumption from the drag of a solid tailgate.
For our project, we used a solid rear axle and suspension from a compact FWD Chevrolet Sprint, which has single-leaf rear springs. We found later on that we had to add
helper springs to accommodate heavier loads with the
trailer. The 4x8-foot size allows for a fairly heavy load. We
just bought two more Sprint rear springs at the local do-ityourself wrecking yard, cut the eyes off each end with a
friend's plasma cutter and used these as an extra leaf on
each side. This increased the load capacity without making

9.9 With the remains of your original centerline in alignment,
clamp the axle ends together with a piece of new heavy-wall
tubing the same size and keep them all in alignment with a
length of wide angle-iron.

9.7 Grind the paint from the center of the axle,
mark a straight centerline across the axle for
lining-up purposes later on and cut the axle
with a hacksaw. A hose clamp around the axle
is used as a saw guide to keep the cut straight.

9.8 This axle is heavy-wall tubing, and, since we wanted good
weld penetration for strength, the cut ends were beveled with
a grinder. Tube at left has been beveled to about half
its thickness.

9.10 Here the assembly is tack-welded at several points
around each joint with a MIG welder.

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Haynes Welding Manual

9.11 When the axle is securely tacked at several points,
remove the angle-iron and make a strong weld bead all
around the axle at each joint. Check for straightness after it
has cooled off.

9.13 We used what materials we had, with 2x3-inch tubing for
the two main rails and 2x2-inch tubing for the rest. When
joining tubing of different sizes, cut one to a standard 45degree angle (here the 2x3), then lay the next piece in,
square it and mark along the second tube for the correct
angle to cut it.
9.14 You can cut tubing and angle-stock with a hacksaw, but
it is tedious. We borrowed a Milwaukee Port-A-Band
hand-held bandsaw that made short, accurate work
of fitting our tubing.

9-4

9.12 If your driveway or shop floor is flat enough, lay out your
pieces of tubing on the ground and check all your
measurements. Cut your joint angles carefully, and, with the
pieces laid out, measure diagonally from corner to opposite
corner to see if the frame is square. Check this again several
times during the tacking and welding phase, too.

it too stiff when unloaded. Since you are using an automotive axle, it comes with brakes and all, and you could hook
these brakes up to your tow vehicle with parts available
from a trailer supply store. For our loads, like firewood, furniture and camping equipment, it didn't seem necessary.
You could also buy a regular trailer axle with springs and
brakes, but they are rather expensive if purchased new.
There's a number of straight rear-axle assemblies available
from front-wheel-drive cars in wrecking yards at reasonable
prices.
There are few hard-and-fast rules in building a trailer,
except that you should design it with the suspension and
axle located in the rear 50% of the basic frame, not in the
center, to maintain good tongue weight up front. Your
tongue weight should be roughly 10% of your total trailer
weight statically at ride height. The one thing that will certainly make a trailer handle badly is not having a long

Haynes Welding Manual

9.20 Put bushings in the front spring eyes and use
cardboard to make up a template for four frontspring-eye mounting plates to be welded to the frame

9.21 After flame-cutting, torching or plasma-cutting your plates, sand
the edges smooth and stack them together with a vise-grip clamp.
You can drill all four plates at the same time, saving time and
ensuring that all have the spring-bolt holes in the same place.

9.22 The front spring-mounting plates are bolted onto either
side of the front spring eye, squared to the rails and clamped
lightly in position for tacking.

9.24 At the rear, short lengths of
heavy-wall tubing, with an insidediameter that fits the spring
bushings, are welded to the
underside of the rails (tack first,
then remove the bushings to finish
welding). Tubes should be
positioned to have the spring
shackles straight up and down.
When the weight of the whole trailer
is put on, they will arc to the rear
enough for easy spring action.

9-6

9.23 After some solid tack-welding, pull the springs out so
the bushings don't melt, and fully-weld the four front spring
mounts. Here the springs are bolted back in.

Building a utility trailer

9.25 In our case, the frame was built just the right size to
use an uncut 4x8-foot piece of 3/4-inch plywood for the
trailer's floor.

enough tongue on the front and, therefore, not enough
tongue weight. When loading your utility trailer, try to load
the heavier items toward the front of the trailer.
When making joints in tubing, angle and other materials, get as tight a fit as you can before welding. A tight joint
will always weld up as a stronger unit than something with
gaps to be filled. If you are cutting with a hacksaw, use a
carpentry miter-box to start your 45-degree cuts at the right
angle. When you're done, give the whole thing a coat or two
of rust-resistant paint, get an assigned registration number
and license plate at your local Department of Motor Vehicles, and you're on your way.
When your trailer is complete, have a qualified weldor/metals expert inspect it for strength and safety. Then
find some things to move!

9.28 Having metal around for welding projects can pay off
when working with wood, too. Use an extra length of straight
angle-iron or tubing to clamp down on a piece of plywood as
a saw guide, for perfectly straight cuts.

9.26 Locate where your tubes are and drill through the
flooring and tubing, then bolt the floor down with carriage
bolts, with the round heads on top so the floor is relatively
smooth and a furniture dolly will go over the floor easily.

9.27 Four posts of heavy 1x2-inch angle-iron were welded
on, one in each corner, as supports for the plywood sides.
After welding, all were checked with a square.

9.29 The front panel is attached with carriage bolts through
the angle-iron posts. The posts were pre-drilled before
welding on, because they are much easier to drill in a drillpress than once they are welded in place.

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Haynes Welding Manual

9.30 Short strips of 1/8-inch thick, 2-inch-wide strap
metal (pre-drilled) were welded along the floor edges to
help attach the bottom of the side panels. When MIG
welding outdoors with argon gas shielding, use pieces of
plywood around you to form a wind barrier to keep the
gas from blowing away as you weld.

9.31 Plywood sides are bolted to the end pillars and the
side plates.

9.32 At the local trailer supply
store, we found a wide variety
of lights, wiring harnesses,
plugs and hitch parts to
complete our utility project.

9.33 The taillights were bolted to the rear angle posts,
but with a short extra piece of steel added on to move
the lights further outboard to clear the tailgate.

9-8

9.34 We originally had the hitch bolted to the main tongue, but
found we had a better tongue weight with the tongue down
another two inches. Simply welding on another piece of 2x2-inch,
heavy-wall tubing set the trailer just right.

Building a utility trailer

9.35 Every trailer needs a safety chain, check with your
local DMV to see if your trailer qualifies for just one,
due to light weight, or needs two to be legal. Take one
end link, grind it clean of any plating and weld it to the
trailer tongue (at top here). Below you'll see the
removable snap-link that hooks to our tow vehicle.

9.37 With the wingnuts undone, the hinged tailgate
folds down as a ramp for furniture dollies,
lawnmowers, etc. The trailer should be hooked up to
the tow vehicle before you step on the tailgate/ramp,
or the lightweight trailer could tilt quickly.

9.36 Our metal tailgate will save fuel because air flows through it on
the road, cutting wind resistance. The frame was made of 1x1-inch
tubing, to which was added steel mesh. Hinges (bottom arrows)
were welded to the tailgate and bolted to the trailer. Top arrows
indicate where tabs were welded to the gate for bolting with
wingnuts to the trailer structure.

9.38 A 4x8x2-foot utility trailer actually hauls a lot of "stuff". We've
known people who built a simple trailer just to make a long-distance
household move, then sold the trailer when they got there, saving
considerably on what a rental trailer would have cost.

9-9

Glossary of welding terms
AC Current - Alternating current, such as in homes and businesses. Polarity
switches at 60 cycles per second (US).
Acetylene - A highly flammable gaseous hydrocarbon fuel used with oxygen
in gas torch welding/brazing/cutting.
Alloy - A modified metal made by combining a base metal with other metals
or chemicals to produce a metal with different properties.
Amperage - A measure of electrical power. In electric welding, such as TIG,
MIG and arc, the higher the welding amperage, the more heat is generated at
the arc.
Annealing - A process of heating a metal and slowly cooling it to soften it
and make it more workable.
Arc Welding - An electrical welding process in which a consumable, fluxcoated electrode rod makes an arc with the work. Also called stick welding.
Arc welding deposits a coating of slag over the seam, which must be
chipped off after it cools.
Acetylene bottles

Alloy numbers on aluminum

Arc welding

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Arc Blow - A phenomenon in electrical welding where the magnetic forces in
the work can cause a wind-like force that blows shielding gasses away. Usually happens in corner welding and can be avoided by switching polarity or
moving the ground clamp.
Argon - A colorless, odorless inert gas often used as a shielding gas in TIG
and MIG welding.
Backfire - A loud pop heard at the torch in oxy-acetylene welding that indicates combustion has backed up into the torch. A potentially dangerous
phenomenon caused by holding the torch too close.
Base Metal - In alloying, this is the pure metal before alloys are added. In
welding, this refers to the work metal, as opposed to the filler metal melted
in.
Bead - The seam between two pieces of metal that have been fused by
welding. The bead usually looks like a tight series of overlapping circles or
ovals of metal.

Argon bottles

Brazing - A type of metal-joining where the parent or base metal isn't melted
but is heated only enough to melt a filler metal such as brass, which holds
the parts together after cooling.
Butane - A fuel gas sometimes used with oxygen for brazing or soldering.
Butane does not produce as much heat as acetylene.
Burn-Through - When the welding flame or arc is too hot for the material,
holes develop in the seam.
Butt Weld - The most common joint in home/shop welding, where the two
edges to be joined are lying flat in front of the weldor.
Carbon - A non-metallic basic element that is a key ingredient in alloying of steels. Higher amounts of carbon
in a steel make it tougher.
Carbon-Arc - A type of welding in which two carbon
rods are brought together to create an arc independent
of the parent metal. A process virtually obsolete in
home/shop welding today.
Carburizing - In welding, an oxy-acetylene flame that is
rich in acetylene, used to coat parent metals with soot
before annealing. In metal work, a process of treating a
surface such as a tool or knife edge by adding carbon to
a hot metal, increasing surface hardness.

Brazing

•
•
•
•

Cast Iron - A common metal, formed of steel with very
high carbon and silicon content, in which soft graphite
flakes appear throughout. The graphite makes the material hard to weld, but it is commonly used in large castings such as automotive engine blocks, heads and
crankshafts, as it is inexpensive to
manufacture and resists vibration
welding current is too high.
damage.
gap between the metal is too wide.

The
The
The speed of the gun is too slow.
The gun to base metal distance is too
short.

Burn-through

GL-2

Clad Metals - Usually mild steel alloys coated with another metal,
such as galvanized steel, or sandwiched with another metal such as

Glossary of welding terms

Butt weld

Deposit

kitchenware that has mild steel sandwiched between two layers of stainlesssteel.
Copper - A reddish basic metal that is relatively soft, malleable and is one of
the best conductors of heat and electricity.
Current - The flow of electricity, usually described by its direction of flow (alternating or direct) and strength (amperage and voltage).
Deposit - The addition of new metal to a welding seam by melting in a filler
rod.
Deposition Rate - How fast filler metal is added to a welding seam. Determined by the wire-feed speed in MIG welding, and by the movement of the
hand-held filler rod in gas, arc and TIG welding.
Ductility - A property of a metal that indicates how well it can be hammered
out thin or drawn into a wire. A welded joint that passes a bending test without breaking is said to have good ductility.
Duty-Cycle - In electric welding processes, this is a way of gauging how
long a particular machine can weld before it must be cooled off. It is expressed as a percentage of a ten-minute test period. At a 40% duty-cycle, a
welder can be operated for four minutes, then must be cooled for six. At
100% duty-cycle, such as industrial equipment, the welder can be operated
all the time.
Electrode - In electric welding, a conductive element that makes the final
connection with the work to create an arc of electrical
energy. In arc-welding, it is the rod or stick. In MIG it is
the welding wire, and in TIG it is a tungsten rod.
Eye-Flash- A eye problem that occurs from observing a
welding arc without protective goggles or lenses. Even
brief exposure to the intense ultraviolet and infrared radiation can harm your eyes, causing a burning sensation
that may show up 6-8 hours after exposure.
Ferrous Metals - Any of several metals made from iron
and other elements. Common ferrous metals include
wrought-iron, cast-iron, steel and cast-steel. Magnets
attract ferrous metals.

Electrode - arc rods

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Haynes Welding Manual

Firebrick

Fillet weld

Filler Metal - New metal added to a welded joint by melting in a filler rod or
wire. Most weld seams require filler metal.
Fillet Weld - A joint such as a 90-degree or T-joint, where the weld bead is
filling a triangular-shaped area. Also describes a multiple-pass weld on thick,
beveled plates.
Firebrick- Special fire-proof bricks used in welding as a
non-conductive base on which to set parts to be
welded. Usually larger than common masonry bricks. Do
not use concrete or red brick to weld on, they will crack
or explode from trapped moisture inside.
Flame - The heat-creating, working-end in oxy-acetylene welding/cutting/brazing. The flame, not the torch,
contacts the work.
Flame

Flamecutter - A mechanized gas or plasma torch that is
motorized and follows a pattern, to cut
out repetitive shapes from metal.
Flashback - A situation in gas-welding
in which combustion goes back into
the torch. More serious than a backfire,
it is signaled by a loud squeal, and
should be stopped immediately by
turning off the gasses at their tanks.
Flashback Arrestors - One-way
valves installed in oxygen and acetylene hoses to prevent flashback. All
gas-welding setups should have these.
Flowmeter - A type of gauge for
shielding gasses which indicates the
flow via a colored ball floating in a clear
glass tube which is easier to read from
distance than a dial-type gauge.

Flamecutter

GL-4

Flashback arrestors

Glossary of welding terms

Flux - A chemical compound that
cleans base metal under heat. In brazing, flux prepares the base metal for the
brass to stick to it. Flux is applied as a
coating to arc-welding rods and to wire
for flux-cored MIG welding and is consumed in the arc to produce shielding
gas.

Gas welding

Forge-Welding - A blacksmithing process where two
pieces of metal are heated to the near-molten state and
hammered together, resulting in fusion. Until the late
19th-century, all metals were either soldered, brazed or
forge-welded.
Fusion Welding - Where the edges of two pieces of
metal are brought to a molten state and joined, usually
with filler metal of a similar alloy melted in.
Gas Welding - Using a mixture of oxygen and acetylene
gasses to form a very hot, concentrated flame to heat
and fuse metals.
GMAW - Stands for Gas Metal-Arc Welding, also known
as MIG (Metal Inert Gas welding) and commonly called
wire-feed welding. The process uses a shielding gas
emitted from the torch while the consumable wire is the
filler and electrode.

Molten weld
metal
GMAW

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GTAW - Stands for Gas Tungsten Arc Welding, also called TIG (Tungsten Inert Gas welding), and may be referred to as heli-arc welding, though this is a
tradename. Helium or argon shielding gas emits from the torch, while a nonconsumable tungsten electrode makes the arc, and filler is added from a
hand-held rod like in gas welding.
Ground Clamp - In electrical methods of welding, this is a
heavy cable from the welding machine that clamps to the
work or the conductive metal work table, completing the circuit from the electrode to the work and back to the machine.
Gun - In welding, this usually refers to the "torch," particularly in the MIG welding process. The similarity to a gun is
that the wire "shoots" out of it into the weld bead.
Hardness - A metal property that can be tested by the ability
of the metal to scratch another surface or be scratched. Sensitive equipment is used to measure metal hardness, and the
alloy number of a metal is used as a hardness indicator.
Hard-Surfacing - In arc-welding, a procedure in which many
weld beads are made overlapping, covering a large area. Using special rods, a very hard, abrasion-resistant face can be
added to tools or farm implements.

GTAW

Heat-Affected Zone - This is the area along either side of
the weld that has been changed by the fusion heat. On ferrous metals, it is indicated by a discoloration. In some cases
the metal in this zone may have become weaker than the
joint itself.
Heat Sink - Something used behind or around an area to be
welded, to protect adjacent areas from heat. Wet rags and
moldable, heat-resistant clays are often used around welding
on thin sheet metal.
Heat-Treating - Changing a metal's characteristics of
strength and formability by scientifically heating and cooling
it. The term usually implies making a metal harder.

MIG gun

Small heat-affected zone on MIG weld

GL-6

Heli-Arc - A tradename of the L-TEC company (formerly
Linde), for their TIG welding equipment. The original process
began with Helium as the shielding gas, and the tradename

Heli-arc torch

Glossary of welding terms
came into such wide usage that it is now generic when
used by weldors.
Helium - An extremely light, colorless, nonflammable
gas, used in welding as a shielding gas and in everyday
use to fill balloons.
Hydrogen - Atomically the simplest of all atoms, hydrogen in its normal state is a colorless, odorless lightweight gas that is extremely flammable. In small
amounts it is used in some industrial welding/cutting applications.
Jig - A device used to keep parts in alignment or position during welding.
Joint - Where two parts are joined by welding, or where
two sides of a crack are welded.
Kerf - The width of the cut in metal cutting by torch or
plasma cutter.
Lap Weld - Where two pieces of metal are overlapped
before welding, rather than butted together. Commonly
used in brazing, and to stiffen a joint in thin sheet metal.
Lead - Another term for an electrical cable, such as a
ground lead.

Brazed lap joint

Machine - The power supply for an electrical welding
setup.
Machine Welding/Cutting - When the torch or welding/cutting gun is
moved by motorized equipment rather than by hand, resulting in a more precise weld or cut.

TIG machine

Machine welder/cutter

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MIG

Multiple-pass weld

Malleability - A metal quality indicating how well the material responds to
being shaped by a hammer or forming tools.
Manifold System - Where a number of welding torches are fed by a common source of gasses, such as in an industrial situation or a weiding school.
MIG - Stands for Metal Inert Gas welding, more commonly called wire-feed
welding because the consumable electrode is a metal wire machine-fed
through the gun from a roll.
WHITE CORE

Neutral flame

Mild Steel - Synonymous with low-carbon steel, the most commonly found
and highly useful material, easy to weld, heat and form.
Molybdenum - A modern metal used in alloying, to make steels and stainless steels stronger and more resistant to corrosion. A well known steel alloy
is 4130 chrome-moly which contains molybdenum and chromium and is a
strong material used in aircraft and race cars.
Multiple-Pass Weld - When welding thick plates or repairing large cracks in
castings, more than one bead must be made. The joint is usually beveled first
and the succeeding passes have wider beads until the joint is filled.
Neutral Flame - In oxy-acetylene welding and cutting, this is the desired adjustment of the torch flame, with equal amounts of each gas.
Nickel - A metal used in alloying steel and stainless steels chiefly to increase
corrosion resistance and suitability for both very low and very high temperature extremes.
Nitriding - A metal treatment process to surface-harden
certain steels, castings and forgings.
Nitrogen - The main component (75%) of the air we
breathe, nitrogen is an inert gas that can be used as a
shielding gas in welding copper, or as the cutting gas in
plasma equipment.
Normalizing - A heat-treating process that refines the
grain structure in hard steels. It is used when highstrength steels have been welded, to remove stresses.

MIG nozzles

GL-8

Nozzle - A component part of the torch in TIG, MIG and
plasma welding equipment, designed to focus the
shielding gas over the arc.

Glossary of welding terms
Out-Of-Position Welding - Welding whenever the parts are not laid flat in
front of the weldor, such as welding vertically, overhead or horizontally but
perpendicular to the ground.
Oxidation - The deterioration process when metals are exposed to oxygen
through air, moisture and natural or manmade harmful elements, On steel it
appears as red-brown rust, on aluminum it can be a gray-black. To prevent
it, metals must be coated with oils, paints or plating processes.
Oxidizing Flame - In oxy-acetylene welding/cutting, when the flame is adjusted with too much oxygen, identified by a ragged purple outer cone and a
hiss from the torch.
Oxygen - A colorless, odorless, tasteless gas that makes up 21 % of the air
around us. It is essential to combustion processes, and combined with equal
parts acetylene makes a 3315° C flame for welding and cutting.
Penetration - Important in all welding processes, penetration describes how
far into the two pieces of a joint the fusing process extends. Maximum penetration makes the strongest joint.
Piercing - In metal cutting, piercing is the technique for starting a cut in the
middle of the material (such as cutting an interior hole in a piece of plate). It
usually requires slightly different torch procedure than starting from an edge.
Pickling - Treating a metal chemically before welding it. For instance, cad
plating on bolts, chain and other hardware can create
dangerous fumes when welded, plus good contact is
hard to make. Plated parts should be stripped in swimming-pool acid before welding.

Oxygen bottles

Plug Weld - Where a piece of tubing fits inside another
and is welded to it through holes drilled in the outer tube.
Also called a rosette weld.
Polarity - The direction in which electrical current flows
in a welding setup. There is AC, which alternates in 60
cycles per second (US), and DC, direct current, which
can be either straight polarity or reversed polarity.
Porosity - An undesirable quality in a weld, with tiny
holes caused by welding dirty metal, using damp arc
electrodes, or getting a gas torch too close to the metal.

PENETRATION
DEPTH

Penetration

Post-Flow - A setting on a TIG machine allows the weldor to adjust how long after the arc is broken the shielding gas will continue to flow to protect/cool the bead.
Post-Heating - Heating a welded part after the final
welding to relieve stresses.
Pre-Heating - When an entire part, or just the weld area,
is heated with an oven or torch before welded to prevent
thermal stresses and uneven expansion and contraction.
Thick metals and aluminum and iron castings are usually
preheated before welding.
Propane - A fuel gas commonly used in self-contained
torches for heating and soldering plumbing pipes. It can
be used with oxygen to perform welding/brazing on thin
materials.

Pre-heating

GL-9

Haynes Welding Manual

OVERLAPPING BEADS

Puddle

Resistance welding

Puddle - The welding bead in process, as the concentrated area of the parent metal is melted and joined with
molten filler rod. The finished bead is a continuous string
of overlapping puddles.
Rectifier - A major component of many electric welding
machines, the rectifier changes AC input current to DC
output.

BASE METAL
Arc welding rod

Resistance Welding - A method of welding where electrodes are placed on either side of the material to be
joined, and a brief arc is made, which is enough to fuse
the materials together at that point without greatly affecting the area around it. The weld is made by heat and
pressure, and the technique is often used as spot-welding on sheet metal.
Rod - The filler rod in welding processes. In arc-welding,
rod is another term for the coated, consumable electrode. In gas and TIG welding, the filler rod is usually uncoated and hand-fed into the puddle.

Seam welding

GL-10

Glossary of welding terms
Root - The bottom of a weld bead viewed in cutaway. In multiple-pass welding oh thick material, the first bead in the bottom is called the root pass.
Reverse Polarity - In electric welding, the term refers to a DC setup where
the work is made negative, and is called
DCRP. It is the opposite of DCSP, or straight
polarity.
Seam Welding - A procedure used on lightergauge metals where the bead is composed of
overlapping spot welds. Some MIG machines
can be timed to perform seam welds. It is also
used on machine-made welds to join long
seams in sheet metal.
Sheet metal - Thinner metals, such as found
in auto bodies, appliances, heating/cooling
ducts. Usually refers to metals from 12-gauge
to 24-gauge.
Shielding Gas - An inert (nonflammable, nonreactive) gas forced out around a weld procedure to cover the arc area, excluding air and
impurities from the forming weld.

Slag

Shielded Metal Arc Welding - Another term for stick or arcwelding, it is abbreviated as SMAW. The flux coating on the
consumable electrodes vaporizes into shielding gas to protect
the weld.
Short Circuit - In electrical terms, this is what makes the arc
when there is an air gap between positive and negative current
flow. When you plug an appliance that is already switched on
into the wall outlet and there is a tiny spark at the plug's prongs,
this is a small-scale version of the short-circuit that makes electric welding possible.
Slag - Oxidized impurities resulting from welding and cutting. In
arc welding, the slag forms a thick, hard coating over the seam,
which must be chipped off with a pointed hammer. Slag is also
found along the bottom of a cut made by a gas torch.

Spatter

Slope Control - In electrical welding, professionallevel welders have controls that adjust the shape of
the current waves, to weld better on non-ferrous
materials. Slope control can also be used to describe controls that gradually increase current at the
beginning of a weld, and taper off current at the end,
both to avoid cratering.
Spatter - Tiny balls of filler metal stuck to the parent
metal around the weld, spatter is produced mostly
by incorrect welding technique, but in arc welding
spatter is unavoidable. Spatter is also present in
smaller amounts with MIG welding.
Spot Welding - Small circular welds used to hold
light sheet-metal panels together. Usually made
through a hole in the topmost panel and common in
auto bodywork (also see resistance welding).

Spot welding

GL-11

Haynes Welding Manual
Stick Welding - Another term for arc welding.

AC Sinusoidal Wave

Stitch Welding - A seam where welding is done only in
short strips with gaps in between where full welding isn't
required. Better MIG machines have timer controls to
easily do stitch welding.
Stud Welding - An option for some types of MIG
welders whereby a special attachment to the gun accepts hollow studs. The studs are pressed onto a surface where the arc is made, and filler wire welds the stud
to the surface and fills the inside of the stud. A very fast
method of replacing broken studs in exhaust system
work.
Square-Wave Technology - An electronic method of
changing the shape of the AC current wave for improved
welding of non-ferrous metals with TIG equipment.
Submerged-Arc Welding - An industrial process where
the seam is buried under a long, thin pile of flux material,
and a mechanized welder travels along the seam welding underneath the flux pile. The arc is not visible, and
the technique is used often on heavy plates such as in
shipbuilding.

|2110-6-13 HAYNESI

Square-wave technology

Synchronous Control - A type of electronic control
which ensures that each weld will begin at the same
point on the wave cycle, particularly important for consistent spot welds in automatic operation.

Tack Welding - Very short welds made at each end and
the middle of a seam, to hold the pieces in alignment before a full seam is welded. When designing and building a project, it's important to tack-weld everything first before finish welding. You may want to
change something at the last minute and tack-welds can be easily broken off
or cut through to make changes.
Tempering - Steels can be hardened by heat-treating but may become too
brittle. Tempering heats a metal to some degree below the transformation
temperature and then cools it to bring back some toughness in the metal.
Tensile Strength - A measure of a metal alloy's (or welded seam's) ability to
resist being pulled apart.
TIG Welding - This stands for Tungsten Inert Gas welding (see heli-arc).
Titanium - An expensive, strong, lightweight material
used in aerospace and race cars. Special techniques are
required to weld titanium.

APPROX. 30 TIMES
THE PANEL THICKNESS

TACK WELDING POINTS

Tack welding

GL-12

Transformer - A major electronic component of electric
welding machines, it turns high-voltage, low-amperage
line current into low-voltage, high-amperage welding
current.
Tungsten - The non-consumable electrode used in TIG
welding. It is resistant to corrosion and doesn't melt until
6170° F.

Glossary of welding terms

TIG welding

Undercut - A weld defect where too much heat was applied and at the sides of the bead the parent metal is
eroded. Usually accompanied by too much penetration
on the backside of the weld.
Voltage - A characteristic of electrical current that
equals the amps times the ohms (resistance). In welding
machines, input current is usually described in volts,
while welder output is usually measured in amps.
Welder - The machine that makes the welded.seam.
Weldor - The person who operates the welder.
Wrought Iron - A soft form of iron that includes some
slag in its formation. Traditionally the material chosen for
making ornate fences, gates and horseshoes because of
its shapability.

Tungsten

GL-13

Index
Alloys, metal, 2-3
Angle clamp, 8-12
Anti-heat paste, 8-12
Arc welding, 2-9, 4-1 through 4-16
arc welders, AC or DC?, 4-4
beginning, 4-8
choosing electrodes, 4-13
safety considerations, 4-7
the arc process, 4-6
types of joints, 4-11

B
Bandsaw, portable, 8-5
Beginning arc welding, 4-8
Belt sander, 8-8
Bender, 8-7
Blanket, welding, 8-4
Brazing, 3-16
Building a utility trailer, 9-1 through 9-10

Checking your welds (oxy-acetylene), 3-14

Choosing a MIG welder, 5-5
Choosing electrodes (arc welding), 4-13
Choosing wire (MIG welding), 5-14
Clamp, magnetic, 8-5
Cleco clamps, 8-8, 8-9
Copper spoon, 8-4
Cutoff saws, 8-6
Cutting (with gas cutting torch), 3-18

Definitions of welding, 1 -2
Development of modern welding, 1-3
Disc sander, 8-7
Duty cycles, 2-17, 4-3, 5-7

Electrode rack, 8-7

Flame adjustment, oxy-acetylene welding, 3-9
Flange punch, 8-9
IND-1

Haynes Welding Manual
Gas welding/cutting, 2-6, 3-1 through 3-26
checking your welds, 3-14
cutting, 3-18
equipment, 3-3
flame adjustment, 3-9
heating, 3-24
how to, 3-9
the process, 3-1
welding with filler rod, 3-11
Gloves, welding, 8-4
Grinder, 8-5
Gun, spot welding, 8-5

how to, 3-9
the process, 3-1
welding with filler rod, 3-11

Plasma arc welding and cutting, 2-18, 7-1 through 7-12
choosing plasma cutting equipment, 7-5
cutting, 7-3
how to use, 7-8
welding, 7-2
Post-flow (TIG welding), 6-6
Practice and training, 2-21
Punch, flange, 8-9

H
Heli-arc welding (TIG), 6-1 through 6-18
Helmets, welding, 8-2
How welding works, 2-2

Rack
electrode, 8-7
materials, 8-11
Rewiring for an arc welder, 4-5

I
Introduction, 1-1 through 1-4

M
Magnetic blocks, 8-12
Materials rack, 8-11
Metal alloys, 2-3
MIG (wire-feed) welding, 2-11, 5-1 through 5-26
choosing a MIG welder, 5-5
choosing a shielding gas, 5-12
choosing wire, 5-14
description, 2-11
learning, 5-16

Safety & shop equipment, 8-1 through 8-12
Safety considerations, arc welding, 4-7
Sandblaster, 8-12
Sander
belt, 8-8
disc, 8-7
Saws
bandsaw, portable, 8-5
cutoff, 8-6
Slope control (TIG welding), 6-6
Spoon, copper, 8-4
Spot weld remover, 8-6
Spot welding gun, 8-5
Stud setter, 8-10

N
Nibbler, 8-9
Notcher, tubing, 8-5

Oxy-acetylene gas welding/cutting, 2-6,
3-1 through 3-26
checking your welds, 3-14
cutting, 3-18
equipment, 3-3
flame adjustment, 3-9
heating, 3-24
IND-2

Table, welding, 8-4
TIG {heli-arc) welding, 2-14, 6-1 through 6-18
aluminum, 6-13
equipment, 6-4
how to, 6-8
post-flow, 6-6
slope control, 6-6
Trailer, utility, building, 9-1
Training and practice, 2-21
Tubing bender, 8-7
Tubing notcher, 8-5
Types of welding, 2-1 through 2-22

Index
U
Utility trailer, building, 9-1

w
Welding
Arc welding, 2-9, 4-1 through 4-16
arc welders, AC or DC?, 4-4
beginning, 4-8
choosing electrodes, 4-13
safety considerations, 4-7
the arc process, 4-6
types of joints, 4-11
blanket, 8-4
definitions of, 1-2
development, 1-3
helmets, 8-2

how it works, 2-2
MIG (wire feed) welding, 2-11, 5-1 through 5-26
choosing a MIG welder, 5-5
choosing a shielding gas, 5-12
choosing wire, 5-14
oxy-acetylene (gas), 2-6
plasma arc, 2-18
safety considerations, arc welding, 4-7
table, 8-4
TIG (heli-arc) welding, 2-14, 6-1 through 6-18
aluminum, 6-13
equipment, 6-4
how to, 6-8
post-flow, 6-6
slope control, 6-6
types of, 2-1 through 2-22
wire-feed, 2-11
with filler rod (oxy-acetylene), 3-11

IND-3

Sourcelist
Airco Gas and Gear
BOC Gasses
575 Mountain Avenue
Murray Hill, NJ 07974
Daytona MIG
1821 Holsonback Drive
Daytona Beach, FL 32117
Eastwood Company
580 Lancaster Avenue
Malvern, PA 19355
HTP America
261 Woodwork Lane
Palatine, IL 60067

Lincoln Electric Co.
22801 St. Claire Avenue
Cleveland, OH 44117-1199
L-TEC Welding & Cutting
Systems
The ESAB Group
P.O. Box 100545
Florence, SC 29501 -0545
Miller Electric Mfg. Co.
718 S. Bounds Street
Appleton, Wl 54911

SL-1



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