transferred to the egg crate cardboard in
pared to the profile gauge reading. And
pencil. Then, the profiles marked on the
some diagonal profiles were indicated as
The hood scoop was measured
cardboard were cut out, and the slots of
a check of overall accuracy.
longitudinally and laterally to
the egg crate were fitted together.
This type of model can be made out of
create its footprint diagram. The
The assembled model yielded a use-
many materials, like plastic or metal,
tape grid was drawn on to, and
fully faithful three-dimensional facsimile of
depending on the situation’s requirements.
then cut into, the egg-crate
the hood scoop.
When metal egg crate models are made,
model’s ribs. Indexing numbers
There were some other steps and
they can be soldered or welded together,
and letters identify each rib. Guide
nuances that are not shown in the accom-
and wil retain their accuracy permanently.
marks on the tape strips identify
panying photographs. For example, each
This is a great advantage when a part has
which of their edges are pertinent.
long cardboard piece (yellow) was
to be formed several times.
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
43
C H A P T E R 5
FORMING, FITTING AND SMOOTHING
This chapter covers shaping, fit-
ting, and smoothing sheetmetal with
hand tools and power forming
equipment. These are the operations
that turn flat stock into the finished
shapes that you need and want.
Simple Tools and Equipment
Most autobody metal work is
performed with relatively simple and
traditional tools like body hammers
and dollies. Add a few really straight-
forward but clever tools that speed
work and enhance capabilities, and
you have the basis for tackling most
While various machines can speed autobody metal repair and forming
projects in this field.
operations, the good old hammer and dolly are still the basis for much of this
Beyond that, there are several
work. Learn to use them properly, and you will have two great friends for life.
expensive, specialty tools and
machines that greatly increase the
While the old masters of the
tion of the time that they required,
speed of working with sheetmetal,
metal crafts were able to hand ham-
and with no loss in quality. But that
and add capabilities that are
mer some very complex panels, or at
kind of equipment is exotic and very
beyond what is possible with sim-
least parts of them, and join those
expensive, and it only applies to
ple tools. For example, the use of
parts together with welds, this kind
advanced projects.
expensive tensioning machinery to
of work is so skill intensive and time
Machines like Pullmax formers,
pull out and to straighten large
consuming that there are only a
fitted with Steck and Eckold shrink-
panels, like the sides of vehicles,
handful of shops left on our planet
ing/forming heads, cost many tens
can produce results that are either
with those capabilities. Advanced,
of thousands of dollars. They can
impossible or prohibitively time
modern metal-forming equipment
accomplish truly wonderful things
consuming if you try to achieve
has made it possible to accomplish
with incredible speed, compared to
them with simple tools.
what those old masters did in a frac-
simple tools. They also require
44
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
FOR M I NG, F IT TI NG AN D S MO OTH I NG
Here is a Pullmax power former, fitted
The Eckold shrinking/forming heads
with Steck shrinking/forming heads.
mechanically gather metal as they press
This Pullmax power former is one of
The backs of the forming dies deform
the most sought after and versatile
metal in a V-configuration. Then, the
smoothes it, which allows the machine
machines in the custom metal-forming
fronts of the dies (not visible here)
operator to form it. The process works
universe. It operates quietly and allows
flatten the V-formed metal. This
when the heads close on the metal,
for many types of operations that
causes local upsets that quickly and
gripping it, and mechanically move
move metal with great precision.
radically shrink and form sheetmetal.
laterally toward each other.
tremendous skill to operate. Sure,
equipment, but that those limita-
its plastic limit in the process of fab-
anyone can shove sheetmetal into
tions are pretty far out on the scale of
ricating it, this must be counteracted.
one of these devices. But to know
projects that people working with
That is, the metal must be shrunk.
when and where to use them, at
autobody metal usually encounter.
This is done by upsetting it, literally
what settings and with what material
Before you pine for some expensive
compacting it into itself, so that
movements, and for how many
metal working machine for a specific
some of its lateral dimension can be
cycles, are issues that require a great
job or task, consider if it can be done
exchanged for increased thickness.
deal of experience to get right.
acceptably with the tools that you
The opposite is also true. If metal
While there are limits to what
already have, or can access.
is shrunk in a collision or in fabrica-
can be done with the simple tools I
tion, by being deformed while it is
mentioned, those limits are often
Applying Plasticity/Elasticity,
under compression, then upsetting
beyond what many metal workers
Work Hardening
occurs. This amounts to shrinking.
assume. It is hard to communicate
and Annealing
Areas affected by this kind of shrink-
these limits in specific terms because
ing must be stretched back to the
they vary with individual skills and
The characteristics of plasticity,
point where they can assume their
aptitudes, but I’ll take a stab at it:
elasticity, and work hardening were
correct shapes.
Generally, if you have to make some-
discussed, in detail, in Chapter 1.
Elasticity is the ability of metal to
thing like a complete fender, or most
Here, we wi
ll see how they apply to
bend, up to a point, and then return
of one, for a 1930s automobile, or
actual metal work.
to its original format by simply
the nose section for an AC or Ford
Plasticity is the characteristic of
releasing it from the force(s) that
Cobra, that work is best left to people
sheetmetal that allows it to be
bent it, or that are holding it in its
with advanced skills and equipment.
deformed without breaking. This
modified shape. This ability of metal
However, if you need to form one
characteristic comes into play when-
to remember its last stable configura-
side of a cowl for that 1930s auto-
ever its shape is changed. If metal’s
tion is an important ally for anyone
mobile, it should be possible with
plasticity is exercised under tension,
working with sheetmetal. It is often
fairly basic tools and devices.
such as die stamping it into a panel,
referred to as memory.
In general, remember that there
it will be stretched. This is normal.
Work hardening is the character-
are limitations to what can be done
However, if metal is deformed in a
istic of metal that causes it to become
without highly advanced skills and
progressively harder to deform in
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
45
CHAPTE R 5
to be hit directly against the dolly,
which would re-stretch it. In the tra-
ditional torch-shrinking method, a
damp sponge may be applied to the
shrink spot to quench it. That stops
the shrinking, and controls the result
of the operation. When using this
shrinking technique, it is common
to use a pattern that groups five
spots (four of them around one in
the center).
This method takes some practice,
but works well. Other methods of
shrinking include serrated spinning
The second step in torch shrinking is
discs mounted in body sanders or
The first step in torch-shrinking metal
to lightly hammer down the heated,
grinders. The disc’s serrations impact
is to heat a small spot to bright red.
bulged spot, with a dolly behind it.
and heat metal at high spots. These
This causes it to pop out as the hot
This piles the metal into itself,
combined actions, heating and
metal expands. But it cannot spread
causing an upset that shrinks it. As
impact, tend to upset and shrink
beyond the heated spot, laterally,
the metal cools, it can be quenched
these high spots—but not necessarily
because it is bounded by unheated
with a damp sponge or rag to
stretched spots. There are also
and unyielding metal.
moderate the shrinking.
numerous shrinking attachments for
MIG and resistance (spot) welders
those area(s) where its elastic limit is
body hammer, while it is supported
that work with varying effectiveness
exceeded as its shape is changed.
by a dolly that is held behind the un-
to shrink metal. For mild shrinking,
The applications of the rules of
bulged metal surrounding the heated
there are hammers and dollies that
plasticity, elasticity, and work hard-
spot. The bulged spot is hammered
are patterned, or that actually move
ening are critical in any but the sim-
back to level with the panel, but no
parts of their surfaces, to pull metal
plest work with body metal. Each of
further, as this would cause the metal
together as it is hit and to upset it.
these factors would become an insur-
mountable obstacle if it could not
be counteracted relatively easily—
fortunately, it can be.
Stretching is the most common
problem in autobody work. Correct-
ing it requires shrinking the metal in
the affected area. There are various
approaches to doing this. The tradi-
tional method is to heat a small area
of the stretched metal—an area
roughly between dime and nickel
size—with an oxyacetylene torch to
red hot. It is heated until a combina-
tion of its expansion, and its being
bounded by the unheated and
The serrated hammers (left) and the dolly (front) cause minor shrinking when
unyielding metal that surrounds it,
they impact metal. The disc (center) causes heating and impact when it is
causes it bulge up. The bulged area is
rotated at high speed against metal, shrinking it. The hammer (right) employs
then quickly hammered down with a
a central face to hold metal and a rotating rim that gathers it.
46
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
FOR M I NG, F IT TI NG AN D S MO OTH I NG
to use it. When you have done this,
you will find that annealing will join
shrinking and stretching as one of
your best allies in metal work.
Hammering Techniques
that Work
Hammers and dollies are the
basic tools of sheetmetal work. Ham-
mers vary in size and configuration.
They range from configurations that
are flat, to those that are highly
This old planishing hammer can form
Bending the two corner areas of this
crowned, and from square faces to
metal quickly, but with limited
fabrication requires moving the metal
round faces. There are also pick ham-
accuracy. Think of it as a massive
beyond its plastic limit. The solution is
mers, designed to raise small areas of
stretching machine that thins the
to bend it part way and then to anneal
metal in very small increments, and
material that it impacts, causing it to
it with a torch. After that, it can be
specialty hammers for accessing
stretch and contour.
hammered down to where it belongs.
hard-to-reach areas, or for perform-
ing special jobs like door skinning.
The hardest things about shrink-
ing it thinner and, thereby, laterally
Hammers should have smooth,
ing are to know where to shrink, and
broader. You can do this by hitting it
clean striking surfaces, to avoid scar-
how much to shrink. Unfortunately,
between a body hammer and a dolly,
ring what they hit. Good hammers
something called false stretch com-
or with a planishing hammer, or
pounds this difficulty. Basically,
other type of power hammer.
where you see a bulge or wave in
Work hardening may progress to
metal may not be the origin point
of
the point that metal becomes so hard
an apparent stretch. What appears to
and resistant to further movement
be a stretched area in a panel may be
that it fractures rather than yield to
set up by an actual stretch that is
your attempts to change its shape
many inches away from an apparent
with tools like hammers. When this
deformation. Your experience will
happens, the solution is to anneal it.
help you to learn to deal with this
This reforms its crystalline structure
issue. For now, be aware that it exists.
to make it soft and workable again. It
In metal work, shrunk or upset
is done with steel panels by heating
metal probably is not as common as
the metal with an oxy-acetylene
stretched metal, but it can cause sim-
torch to a temperature between 1,550
ilar havoc in the shape of a panel.
and 1,600 degrees F (between bright
Shrunk metal is often a result of the
red and salmon red), and allowing it
upsetting of an area(s) of a panel in
to air cool. Sometimes, depending on
The first four tools (from the bottom
the course of dinging dents out of it.
the metal and the situation, it may be
up) are general-purpose combination
Removing upsets of this sort is
advantageous to apply a damp
body hammers, in various crowns.
refreshingly simple, again involving
sponge to the annealed surface, after
The fifth is a door-skinning hammer.
an exchange of lateral dimension for
it has cooled substantially, to slightly
The sixth is a low-crown hammer,
thickness. And, again, knowing
enhance its stiffness, and to give it
with both round and square faces
where to stretch metal is more diffi-
structural strength.
(the latter is for working up to flat
cult than stretching it because
You will need to experiment with
edges). The seventh tool is a hammer
stretching metal only involves mak-
annealing to master when and how
for fender dinging.
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
47
CHAPTE R 5
Some jobs are best performed
with specialty hammers like those
with rubber, rawhide, or plastic
heads. Choosing the right hammer
for a task involves both experience
and personal preference.
Dollies are used to support metal
that is being hammered. In some
cases, such as in tight-access situa-