by Matt Joseph
purposes. Beyond certain tempera-
For the record, work hardening
broke. Do you remember that it felt
tures—different ones for different
occurs because steel has a granular
warm at the place where you were
metals and alloys of metals—the
structure. Bending it rearranges and
bending it, before it broke? That
grain structures of metals rearrange
distorts its grains. Beyond a certain
heat was generated by the friction
themselves and eliminate work-hard-
point, this becomes difficult, and
of the grains in its structure
ening effects. This process is called
somewhere beyond that, the steel
deforming and riding against each
annealing, and only works if sheet-
will fracture; that is, it will reach
other as you bent the paper clip
metal air cools slowly, after being
and exceed its plastic limit. Maybe
back and forth.
heated to its critical temperature. In
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
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CHAPTE R 1
the case of autobody steel, that tem-
perature is roughly 1,600 degrees F,
which appears as a color between
bright red (1,550 degrees F) and
salmon (1,650 degrees F). How steel
cools, after it has been heated, deter-
mines many of the characteristics of
the hardness that it exhibits. For
example, quenching it (cooling it
rapidly with air, water, or oil) after it
has been heated to its critical tem-
perature, tends to rearrange its grains
in ways that harden it.
There is more discussion of the
effects of heat on sheet steel in later
chapters, with particular regard to
using annealing and quenching to
solve problems caused by work hard-
ening from moving cold metal, and
hardening softened areas near welds.
After a panel is stamped, it may still need detail work. Employees in this 1975
At the Factory and Afterward
GM plant are shown performing some of that work. (Photo supplied by General Motors Corp.)
Autobody panels begin their
lives in near-ideal conditions. Clean,
ally flutter in the wind, and from road
uniform sheet stock was stamped or
vibrations. Stamping imparts strength,
rolled into shape. Huge machines
and helps to eliminate most flutter.
accomplished this work by exerting
Besides, no one would want to drive a
many tons of pressure on flat sheet
car that looked like a steel box.
stock that was inserted between the
When you repair damaged sheet-
drawing and rolling dies of stamping
metal, you must deal with the work
devices. In such operations, flat
hardening that occurred in the origi-
metal is deformed by enormous force
nal stamping or rolling process that
that stretches and shapes it. The
turned flat stock into finished panels,
This twice-mangled fender suffered
metal is clamped at its edges by
and with the additional deformations
two kinds of damage: first a collision,
“binder rings,” and then acted on by
that occurred when it was damaged.
then someone made it worse by
dies that force it into desired shapes.
There is also the factor of road vibra-
trying to repair it. After hammering on
Later, it is trimmed and pierced at
tion, which, over long periods, hard-
it with no good result, he or she
attachment points.
ens panels as they travel down the
decided to cut out some of the
For the metal worker, the impor-
road. It is important to keep all of this
damage, then gave up.
tant thing about these processes is
in mind when you find a panel resist-
that the stretching and forming of
ing your best efforts to change its
edly inept, may have tried to repair
sheetmetal between dies work hard-
shape and restore it to its original
the damage before you. Their mis-
ens it. That is one of the reasons for
configuration.
guided efforts, often with very large
stamping it; to make it stronger. The
One of the worst forms of dam-
hammers and other destructive
other reason, of course, is styling. If
age that you will ever encounter is
devices, may have made things worse
cars were fabricated from unstamped
bad repair work. A range of people,
or much worse than they were. Colli-
sheetmetal, their panels would liter-
from the truly clueless to the dedicat-
sions deform and work harden metal.
14
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
W HAT YOU S HOU LD K NOW B E FOR E YOU START
They also may stretch or upset it. Bad
body work, the kind that roughs out
damage and then gobs filler over
crude work, tends to make these
problems more severe. These situa-
tions will tax the full range of your
abilities, talents, and patience.
Impact is not sheetmetal’s only
enemy as it ages. The other major
problems gather under the brown
banner of corrosion, a.k.a. rust. Rust
is birthed by a chemical reaction
This one is as bad as it looks. Even
One of these air disc sander/grinders
between water and metal. Road salt,
though the destroyed panel is flat and
is an expensive professional model.
an
electrolyte
in
dirty
water,
relatively easy to form, economics
The other is a low-end, almost-
enhances the speed of this reaction.
dictate installing a replacement fender
generic knockoff that is very
Rust occurs when moisture gets
panel, assuming that sound metal can
inexpensive. They are almost identical
through or around paint and other
be found for its attachment.
in performance, and probably in
anti-corrosion surface treatments.
durability. The inexpensive one can
Since water is very adept at infiltrat-
be replaced more than three times for
ing small spaces (through capillary
what the expensive one costs.
action) and at penetrating coatings, it
is a cinch to attack vulnerable areas
need for them, not just because they
like door seams and panel attach-
are there. When that need arises, it is
ment points. A great deal of body
a good idea, in most cases, to stick to
work on cars involves repairing the
top-quality tools—ones that come
ravages of rust. Sometimes, small
from reputable vendors and that will
areas of perforation damage can be
welded shut. More often, panels
There are exceptions to this. Some
require the excision of diseased areas,
air tools, like the die grinders and air
and replacement with sound metal.
disc sanders that are so useful in
autobody work, largely have become
Necessary Tools and
Massive, power forming machines,
disposable tools. Buying good ones
Equipment
like this Pullmax, come in many
with name brands probably is a
brands and configurations. They can
waste of money. Most people I know
Somewhere between having the
be fitted with a variety of specialized
buy cheap ones and replace them as
basic tools for autobody work, and
tooling or with general tooling like
needed. Since the prestige versions of
having the latest, most exotic, and
these Steck power-shrinking heads.
these tools cost between three and
most
advanced
metal-forming
They can form metal quickly, but
five times more than the throw-
devices ever made, there is a happy
really are beyond the needs of
aways, and the repair (tune-up) kits
medium of being reasonably well
most shops.
for them cost as much as the generic
equipped for most of what you
versions of these tools, this makes
encounter. An el cheapo starter
max power forming machine, and a
great sense.
body tool kit, with three unbal-
high-quality TIG welder is almost
However, items like cheap body
anced body hammers and a crudely
certainly way beyond the needs of
hammers or tin shears tend to create
cast dolly, probably won’t take you
novice- or intermediate-level auto-
bad results and should be avoided.
very far in this work. On the other
body metal work.
My general rule is: If something
hand, roaring out and acquiring the
The best approach is to acquire
makes direct contact with metal, like
likes of a good English wheel, a Pull-
tools and equipment as you find the
a file, hammer, or dolly, it should be
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
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CHAPTE R 1
Many small and relatively inexpensive
tools, like these body files, sheet-
metal pliers, and 41⁄2-inch electric
grinder, are endlessly handy for
autobody metal work.
up hammering various shapes, and a
good anvil is essential.
Small items, like sheetmetal pli-
ers and an assortment of hand
shears, are essential when you start
Tools tend to multiply, as if by magic. Most of my hammers, dollies, picks, pries,
this work. A few good body files of
files, and other bodywork hand tools, are mounted on this wall. My wife thinks
differing tooth count and some rigid
it’s excessive and, truth be told, I could get by with about 20 percent of them.
and flexible holders for them are
necessary for many jobs.
A good electric disc sander is a
must for doing this work; 7 or 9
inches will do. A small electric or air
hand grinder, 4 or 41⁄2 inches, will be
endlessly useful. Some way of cutting
metal with rotary abrasive wheels is
very desirable. A 3-inch air muffler
cutter can be bought for less than $10,
and fitted with more-useful 4-inch
cutting wheels. Air nibblers, shears,
and small reciprocating saws have
become very inexpensive in recent
Each of these metal-cutting tools is very useful. From left to right: electric
years, and are extremely useful in
power shear, air power shear, air nibbler, air power shear, hand nibbler, hand
this work.
shear, air hack saw, and two air disc grinders in different disc sizes and
A good MIG welder and an oxy-
configurations.
acetylene torch are highly desirable
for performing many bodywork
top quality. Otherwise, evaluate the
assortment of hammers and a few dol-
tasks. Likewise, a good plasma arc
economics of replacement strategies
lies. The hammers should have faces
cutter is a great asset. You might
for tools that don’t contact the metal.
of various crowns, sizes, and shapes. A
want to put these items on your wish
To get started in autobody work,
set of soft hammers, say plastic and/or
list, if you do not already own them.
you need some basic hand tools for
rawhide mallets, is a great addition. A
As you do more fabrication work,
shaping metal. I recommend an
shot bag is a good item to have to back
you will want a metal shear, a slip
16
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
W HAT YOU S HOU LD K NOW B E FOR E YOU START
As you advance in this work, you find
that you need a good oxy-acetylene
torch setup. No other source of high
When it comes to welding sheetmetal,
This old, air-percussion fender-
heat, like propane or oxy-propane,
a MIG welder is the best all-around
smoothing hammer is very useful for
has the versatility of oxy-acetylene.
bet. The TIG welder does finer work
rough-forming metal. Modern
While you can weld panel metal with
with less distortion, but the
versions of it start at $50 and
oxy-acetylene, there are better ways
equipment is expensive and the skill
escalate to more than $1,000. In any
to do it.
level needed is higher.
price range, it is well worth having.
The modern name for this tool is
This device combines
planishing hammer.
the features of a slip-
roll (top), a finger
brake (mid-section),
and a shear
(bottom). It performs
all three functions
reasonably well, but
not as well as the
individual, dedicated
tools. Still, for a few
hundred bucks, you
get great capability.
roll, and a metal brake. These devices
work. The key to your tool and
vary in quality from expensive to
equipment program is to figure out
very expensive. There is even a com-
what you may need regularly, versus
mon unit that embodies all three
what you will probably use no more
This kind of heavy-metal-forming
functions in one tool and, while it is
than once a year. Purchasing the lat-
equipment, power hammers and large
a bit clumsy, it provides an econom-
ter class of tools can be put off for a
English wheels, is great for
long time. Hey—if you only need to
professional use. For big restoration
good work.
use something once a year, you
shops, prototype shops, and pattern
There are hundreds, maybe thou-
might consider borrowing it.
shops that do forming work in high
sands, more tools and devices that
The main point in acquiring
volume, this equipment earns its keep.
may be helpful in pursuing metal
tools is to avoid the extremes of
For most small shops, it’s overkill.
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
17
CHAPTE R 1
work can often be easily fabricated
from scrap metal.
Tools and equipment tend to be
as good and useful as the person
using them. Don’t waste time spoon-
ing after expensive and exotic stuff.
Great equipment hardly ever makes
it possible to do a job. Usually and at
best, it increases the efficiency of
doing it. Keep that in mind when
you peruse tool catalogs. Many great
sheetmetal fabrications were com-
pleted with very simple tools, in very
simple settings, with planning, skill,
and patience.
Find a happy medium. If you
realize that you badly need some-
It is often helpful to make special tools for jobs like holding work pieces.
thing to work more efficiently and to
These two homemade tools are based on commercial slide hammers. One
get better results, lay your plans to
uses a pair of locking pliers for pulling out things. The other is for bumping
acquire it. But, if you find that you
metal toward you through access holes.
have tools and equipment that you
never use—that’s why there are
under equipping and over equip-
garage sales, classified columns,
ping. If you only have three
Craig’s List, and eBay.
chipped hammers in your reper-
toire, and one of them is a carpen-
General Considerations
ter’s hammer, your metal work will
show it. At the reasonable middle
As you pursue autobody metal
ground, a quality planishing ham-
work, you can often find comfort
mer is a very good investment for a
zones in many of the varied tasks that
wide range of projects. At the
you perform. That is, you find specific
extreme, an old Yoder or Pettengell
ways of doing things that “just feel
power hammer, hulking in the cor-
right,” and that feel better than other