Automotive Bodywork and Rust Repair

by Matt Joseph

  tions against the backs of fenders,

  The two rawhide mallets (lower left)

  they are also used as hammers. Most

  provide soft, yielding surfaces for

  dollies are made of cast iron, and pre-

  Hammering off-dolly is a precision

  moving metal. The lower one is shot-

  sent several different and useful con-

  operation that is used to shape metal

  filled, giving it a dead-blow feature.

  tours for working surfaces. When

  without stretching it. The work shown

  The plastic poly mallets (top) offer

  hammering metal that is supported

  here is a fine-tuning operation, in the

  resilient, shaped impacting surfaces

  by a dolly, there is the critically

  final stages of forming and flattening

  that are great for forming shapes in

  important distinction between on-

  a surface.

  metal without marring it.

  dolly and off-dolly techniques. Work

  on-dolly means that the dolly directly

  result is to stretch that metal. Some-

  have a feel and balance that makes

  supports the metal that you are ham-

  times this might be your object, or

  them natural and comfortable to

  mering and is placed exactly under

  part of it, but sometimes it produces

  swing. They are best swung with the

  and in contact with the area that is

  the unwanted result of stretching.

  arm, from the elbow, with a slight

  being hammered. This means that

  Hammering off-dolly is much

  flexing or unwinding of the wrist. The

  you are hitting the metal between the

  more common, and usually more

  motion against the metal for most

  hammer and the dolly. The inevitable

  useful. In this technique, the dolly is

  procedures should be a slapping

  action that allows rebound, some-

  times with a little bit of sliding thrown

  in. This is not like driving nails.

  Hammers should be held some-

  what loosely, and with a limber wrist

  behind them, to allow them to

  rebound. You should pay attention

  to that rebound because it contains

  information about what is happen-

  ing to the metal that you are ham-

  mering. The sound that a hammer

  makes also communicates informa-

  tion about what its impacts are

  doing to the metal. Most beginners,

  and a few professionals, tend to hit

  too hard with body hammers,

  expecting one or a few master blows

  to move the metal. In most situa-

  tions, it is far preferable to use sev-

  Dollies like these offer many useful surfaces for backing up hammer work. The

  eral lighter blows. Good metal

  three on the left are for working very small areas. The two larger dollies, with

  workers develop distinctive rhythms

  handles, can be mounted in vises and used in fabricating. The front dolly is

  and timbres to their hammer blows.

  rubber clad, and provides a somewhat resilient surface.

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  This photo shows hammering on-

  dolly, but in this case the dolly is

  rubber clad. This allows for fine

  shaping, without much danger of

  stretching the metal. Hammering on-

  Shot bags come in many sizes and shapes, and can be filled with many

  dolly with an iron dolly can cause

  materials. The large, square bag (center) contains lead shot, and is useful for

  excessive stretching, even if you are

  forming fairly large items. The smaller bags (right) are hand held, for backing

  careful to control this tendency.

  up stationary items. The round bag (left) works both ways.

  not held directly under the metal

  rebound action. Various specialty

  Bending, Beading and Prying

  that is hammered, but offset from it.

  dollies are available in many differ-

  An example would be holding a

  ent shapes and, in some cases, are

  The fastest way to move a lot of

  dolly under one or the other side of

  clad in relatively soft materials, like

  sheetmetal in a broad area is with

  a ridge that is being hammered

  rubber, to give them resilience, or

  devices that bend and bead it. Bend-

  down. The result is to level the ridge

  dampening.

  ing and beading apply more to fabri-

  to the panel. There may be some

  Shot and sand bags are very use-

  cation than to repair. Prying, another

  unwanted upsetting of the metal

  ful for hammer forming three-

  form of mechanical bending, is used

  that is hammered this way but this

  dimensional shapes. These bags can

  mostly in repair work. The mainstays

  can be corrected easily, later.

  be filled with steel or lead shot, as

  of equipment for bending body

  Hammering

  off-dolly

  makes

  well as sand or other materials. They

  metal are brakes and slip rolls. Brakes

  good use of the rebounding action of

  are used to back up metal in a some-

  are used to make straight-line bends,

  the dolly, after it is impacted by the

  what yielding manner. As you ham-

  in sheet stock, to very precise angles.

  metal that is being struck against it

  mer metal on a shot bag, it dishes

  They also can be used to radius flat

  with a hammer. After the hammer

  out. This provides relatively smooth

  material by applying numerous, suc-

  blow is struck, the dolly rebounds

  forming and controlled stretching in

  cessive, small bends to it. Finger

  against the metal and acts to push it

  the same operation. Shaped plastic

  brakes, or box and pan brakes, are

  out, toward the hammering force.

  mallets, used with shot-bag backing,

  useful for making bends in local

  For this to work, the dolly must be

  is a particularly effective hand-form-

  areas, with standing metal on one or

  pressed against the back of what you

  ing combination.

  both sides of those bends. Slip rolls

  are hammering. You can easily imag-

  Every autobody practitioner has

  are used to impart permanent curva-

  ine that driving a configuration like

  some favorite backing surface for ham-

  ture in one plane to panel materials.

  a ridge down at its center, while

  mering metal. These can range from

  Bead rollers are specialty tools that

  holding a dolly, alternately, under

  anvils to blocks of various woods, and

  are capable of rolling shallow beads

  each side of the ridge, tends to level

  even plastic materials. One of my

  or other shapes into flat or slightly

  the panel, and remove the ridge. As

  favorite b
ackup surfaces is between

  curved sheetmetal.

  the ridge goes down, the metal bor-

  one and three thicknesses (layers) of

  Picks and pries are used locally to

  dering it is kept level by the dolly’s

  heavy, corrugated cardboard.

  move metal, particularly in poor

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  CHAPTE R 5

  This 16-foot sheetmetal brake is beyond the needs of most situations. It can be

  Hand-operated bead rollers, like this

  used for making bends in small items, too, and operates with an ease and

  one, form beads and ribs into sheet-

  precision that are wonderful. The counter balances make it very easy to control.

  metal. Numerous forming and folding

  dies are available for bead rollers.

  Some of the more interesting

  combinations use a soft top die and a

  hard bottom one.

  amount of force and frequency of its

  application. This realization led to

  some pretty violent devices for form-

  ing metal. The most famous of the

  early versions of these were the Pet-

  tingell and Yoder power hammers.

  These were huge, noisy devices that

  used

  a

  wide

  variety

  of

  shaping/stretching dies to greatly

  speed the process of custom forming

  metal.

  Over the years, power hammers

  evolved into much more compact,

  quiet, and effective machines. Fore-

  most in the modern crop of such

  devices is the Pullmax, a machine

  This finger or box-and-pan brake provides for bending around three-

  used widely in prototype and

  dimensional features of metal. It is shown here making a bend that would be

  advanced metal restoration shops.

  impossible with a flat brake.

  In contrast to the earliest power

  hammers, modern machines, like

  access areas, where hammers and

  Power Forming

  the Pullmax, are as often used with

  dollies cannot reach it.

  the likes of Eckold shrinking dies and

  All of the tools that are used for

  Eventually someone realized that

  Steck shrinking/shaping dies. These

  bending, beading, and prying repre-

  the action of striking metal with a

  are general-purpose heads that can

  sent non-impact methods of moving

  hammer on a dolly could be mecha-

  form and/or shrink metal very

  and modifying metal.

  nized, thereby greatly increasing the

  locally and with no fuss. They are

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  relatively quiet and easy to use. The

  tricky part of the proposition is to

  know when, where, for how long, and

  at what pressure settings to use them.

  Before you add a Pullmax or other

  power hammer to your want list, you

  should know that these are very expen-

  sive machines that are in the province

  of professional, not amateur, use.

  Pulling Approaches to

  Moving Metal

  So far, most of our attention has

  been directed toward hitting metal

  down with a hammer, or using a

  dolly to hit or rebound it out. There

  are also times when it is desirable to

  pull metal. These situations are some-

  times encountered in repair work. In

  Pries and their close cousins, spoons, are used in many operations. The more

  the most elaborate processes, pulling

  robust items shown here, spoons, do prying duty or provide hammering backups.

  plates are soldered, brazed, or welded

  The lighter items are used only for prying. The homemade edge bender (top) is

  to areas that require massive pulling

  an item I fabricated from an old car spring.

  force to return them to something

  close to their original positions. Then

  mechanical or hydraulic force is used

  to pull them out by the plates. This is

  very heavy duty repair work that

  requires considerable equipment.

  Smaller scale pulling is commonly

  performed to remove dents, where

  most of the displaced metal is locked

  out of position by a very small area of

  metal, and where access issues prevent

  using impact tools to push out that

  small area. Manual and mechanically

  activated suction cups can be used for

  very light duty pulling. Some shops

  employ the barbaric practice of using

  a slide-hammer to push or puncture

  (or shoot) a hardened screw through

  an area of a panel that is to be pulled.

  Then, the screw is tightened into the

  metal by turning it, and the slide-

  Slip rolls, like this hand-operated machine, provide for uniformly bending

  hammer is operated in the other direc-

  metal in one plane. They impart predictable and continuous curves to sheet-

  tion to pull the metal out by the screw.

  metal. Slip rolls can also be set to put several different curvatures in the same

  Avoid this rough approach.

  panel, and to flatten distorted metal.

  A more refined version of this

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  CHAPTE R 5

  practice is to use a stud welder to

  weld a steel stud to a depressed area

  of a panel, and then to use a slide-

  hammer with a special clamp, that

  holds the stud’s head, to pull the

  metal out. When this operation is

  finished, the stud can be ground

  level to the panel.

  Smoothing, Stretching,

  Shrinking and Forming

  Operations

  Two of the simplest machines

  made for metal working, the English

  wheel and the planishing hammer,

  are extremely useful for basic fabricat-

  ing jobs. These exist in both relatively

  inexpensive and high-end versions.

  English wheels were among the

  earliest applications of machines to

  Stud welding involves using a specialized spot welder to resistance weld the

  head of a stud to part of a panel, for the purpose of pulling its metal out. The

  welding operation is very fast.

  Once the stud is welded to the panel, a

  specialized slide hammer grips its

  shank. The stud is then slide hammered

  This stud-welder attachment is great for pulling up small dings. The tool’s copper

  away from the panel, pulling out the low

  tip is resistance welded to the ding’s center, and then pried away from the panel

  metal. The stud is then twisted or cut

  with the tool’s levers. When the area is level, the tool is twisted slightly to break the

  off, and the area is ground flat.

  weld, and removed.

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  wheeled metal. Stroking the metal

  through the wheels at
different angles

  makes it possible to form almost any

  curved or dished shape. It takes con-

  siderable practice to know where, with

  which wheel combinations, with what

  pressures, and for how many strokes to

  use an English wheel. When you begin

  to learn how to determine and com-

  bine these variables, it is amazing what

  you can accomplish with this simple

  device. Wheeling is often performed

  after some kind of impact procedure,

  like hammering metal into a shot bag,

  has been used to rough out a shape in

  it. In these cases, wheeling can fine

  tune the format of the metal, and

  These old fender-smoothing tools amount to portable English wheels.

  smooth out the results of the impacts

  Although they date from the days of the Model T Ford, they are still useful in

  used to form it before it is wheeled.

  some situations. They are intended more to smooth than to stretch metal.

  Unlike the power hammering

  metal forming. While these devices

  are only powered by human muscles,

  knowledge, and imagination, they

  are almost always larger items than

  can be hand held, and are incredibly

  useful for stretching, forming, and

  smoothing metal for fabrications.

  The basic device is a C-clamp-

  shaped unit with two opposing

  wheels that can be incrementally

  tensioned against each other. The

  wheels usually differ in diameter,

  while the tension between them is

  adjustable. The top wheel is gener-

  ally flat, and much larger than the

  bottom wheel. The bottom wheel

  usually has varying degrees of lateral

  curvature, and is almost always avail-

  able in different contours.

  The principle of the English wheel

  is that as metal is pushed and pulled

  between

  the

  tensioned

  wheels,

  the pressure stretches and forms it. The

  curvature—and thus the contact patch

  area and resulting pressure—of the

  This imaginative wheel combination, mounted on an English wheel, uses a

  shaped wheel helps to determine creasing lower wheel and a soft upper wheel, literally a caster wheel. The

  the contour that is worked into the

  result is to allow forming without excessive stretching.

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  CHAPTE R 5

  English wheels

  devices mentioned earlier in this

  come in many

  chapter, English wheels vary from