Automotive Bodywork and Rust Repair

by Matt Joseph

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

  against and grip it. This upsets and

  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

  collision, or if it is stretched beyond

  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-