Automotive Bodywork and Rust Repair

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

  13

  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
/>   last for the rest of your working life.

  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

  15

  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
/>   ical approach to doing reasonably

  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