Automotive Bodywork and Rust Repair

by Matt Joseph

been pushed in, and where there is

  come. The second solution, which

  getting bumping right can save sig-

  insufficient room to swing a hammer.

  takes skill and practice, is to use two

  nificant time in metal finishing.

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  AUTOMOTIVE BODY WOR K AN D R UST R E PAI R

  B U M P I NG TO MOVE TH E M ETAL TH E R IG HT WAY

  The Case of Bumping the

  Run Down Spare Tire Cover

  The panel in front was

  clamp a couple of times, and he hit the

  dragged and flattened. The

  wooden ram board with a rubber hammer

  one in the rear is in near

  a few times, for added persuasion. As he

  perfect shape, and can be

  tightened and hammered, he levered up

  used as a model for

  one edge of the panel with a soft pry. In

  reshaping the damaged

  just a few minutes he had the panel

  panel. The Door County

  bumped into pretty good shape.

  Civil Defense Auxiliary

  Next, he checked the profile shape of

  Police sticker on the good

  the tire cover against a template that he

  panel is probably unique.

  had made out of cardboard from a good

  spare tire cover, and found it bent and

  We wil never know who ran down this rubber, plastic, or rawhide malets, I warped in a couple of places. Since the Triumph TR-3 spare tire cover. But

  reached for one of our large dol ies, to

  original accident and our lever press

  my friend, Herb Statz, who worked with me

  begin bashing out the worst of it.

  bumping ministrations had not caused any

  to fix it, had a first-class idea for bumping

  Herb stopped me before I struck with

  upsets or stretches in the panel, a little

  out most of the damage to it in a few easy

  the dolly, saying, “Hey, let me try some-

  careful bumping with a dead-blow plastic

  moves.

  thing.” Then, using some scrap wood and

  mallet returned it to its original format, with

  The cover had been dragged and flat-

  some large C-clamps, he rigged a small

  no further actions needed.

  tened by the time that we received it, and

  metal table as a lever press. In a couple of

  I suspect that if Herb had not inter-

  the license plate part of the panel was

  moves, he had the panel pushed back to

  vened, convincing me to use his lever press

  severely pushed in and leveled. Since the

  its original depth, and pretty well straight-

  method instead of my big-hammer approach,

  damage was too locked-in to remove with

  ened out. He had to tighten the levering

  we would have spent a much longer time try-

  Using some old wood scraps and a

  couple of large C-clamps, it took

  Herb Statz just a few minutes to

  Some of the straightening work

  devise and implement this

  With the basic damage repaired,

  was done with a dead-blow

  makeshift lever press. With a little

  Herb made a cardboard model of

  hammer on the panel’s back, and

  help from a rubber hammer and a

  both sides of the good panel, to

  more was done to reshape its

  plastic pry, he quickly restored the

  compare shapes. He then corrected

  edges. Herb’s technique for

  panel’s basic shape, with no

  the areas of the damaged panel

  removing the worst damage

  collateral damage.

  that were warping it.

  minimized the panel’s warping.

  AUTOMOTIVE BODY WOR K AN D R UST R E PAI R

  59

  C H A P T E R 7

  METAL FINISHING

  In the metal

  and shaving metal off them, to

  finishing stage of

  make small dimensional and curva-

  body work, final

  ture changes.

  panel contour

  For those reasons, I think that

  adjustments are

  metal finishing is the most critical

  made and most

  stage of this work. It may lack the

  surface defects

  visually dramatic outcomes of bump-

  are removed.

  ing, but when it is done well, it is the

  Making a final

  part of metal work that produces

  correction to the

  much of the wow factor in great

  contour of a

  autobody repairs and fabrications.

  sectioned door is

  One copasetic aspect of metal

  shown here. Note

  finishing is that the tools used to

  that Blaine is

  accomplish it are refreshingly few,

  working with his

  simple, and relatively inexpensive.

  sightline aligned

  Of course, there is an offsetting

  with the panel’s

  downside to that proposition: You

  surface.

  have to use those tools correctly to

  get good results, and that is not

  always easy. This chapter focuses

  on the correct use of metal finish-

  ing tools—body files, pick ham-

  mers, and disc sanders—to achieve

  great results.

  Metal finishing is the critical

  faces are filled, just before panels are

  step in preparing metal for painting.

  painted. By its nature, metal finish-

  Indicating, Feeling and Other

  It occurs between the bumping

  ing is finer work than bumping, yet

  Human Tools to Determine

  stage, where metal is hammered,

  offers more latitude for correction

  Panel Surfaces

  pried, pushed, or pulled into shape,

  than the filling stage that follows it.

  and the filling stage, where very

  In metal finishing, you can still

  If you need to change the contour

  small defects in metal-finished sur-

  modify surfaces by moving them

  of a panel, it should be done before

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  AUTOMOTIVE BODY WOR K AN D R UST R E PAI R

  M ETAL F I N I S H I NG

  case with character lines of various

  configurations (for example, 1960s

  phony louvers in some Chrysler

  products’ rear fender flanks).

  It is this feature, the smoothness

  of crowns and combination crowns,

  that metal finishing must preserve. It

  also must level minor surface devia-

  tions, in the form of small bumps

  and depressions. Metal finishing is

  the last appeal in the matter of panel

  crown continuity. It is also very close

  to the last appeal in the matter of

  panel smoothness.

  Unlike bumping, where you can

  sense surfaces visually, and by feeling

  them, metal finishing works at a

  finer level. It works at the edge of the

  ability of the human sense of touch

  These two tools illustrate the difference between bumping and metal finishing.

  to sense deviations, and beyond the

  The pneumatic body hammer (top left) has a 1-inch stroke, for movin
g metal

  capabilities of unaided visual inspec-

  and removing ridges. The pneumatic percussion hammer (bottom right) can

  tion of unpainted metal surfaces to

  pick light metal a few thousandths of an inch in metal finishing work.

  define consistency. The solution to

  metal finishing operations begin. But if

  you need to make sure that a contour

  is perfectly consistent in very small

  dimensions, and that it is contained in

  a nearly perfect surface, metal finish-

  ing is where you get these results.

  Any crown or combination of

  crowns in a panel must flow

  smoothly—by itself, or as one crown

  into another. If the requirements of

  practical matters, like covering up

  vehicle mechanisms, or opening

  doors, requires a panel surface to be

  discontinuous in crown, well, that is

  why stylists employ creases, charac-

  ter lines, and the other discontinu-

  ous or angular ploys and styling

  components of their trade. Some-

  times, I suppose, they do these

  things just for fun. What autobody

  panels do not have is irregular and

  Body files come in many sizes, shapes, tooth counts, and configurations.

  illogical interruptions to the flow of

  These are unusual, special-purposes files. None of them are currently

  crowns, unless such features are con-

  available, but they do show up at swap meets and auctions. There are

  sistent and repeated, as can be the

  situations where they work much better than flat files.

  AUTOMOTIVE BODY WOR K AN D R UST R E PAI R

  61

  CHAPTE R 7

  exceeding those human limits is to

  find deviations with files and disc

  sanders. Once these are located,

  metal finishing procedures work to

  correct them. In the case of low

  spots, the deviations are raised with

  hammers, usually pick hammers,

  and leveled with more filing or disc

  sanding. If the deviations are bumps

  (projections), they are filed or

  sanded to level.

  These are very fine adjustments,

  involving as little as 1 or 2 thou-

  sandths of an inch. In a 20-, 21-, or

  22-gauge panel, there is not much

  thickness to file or sand off, without

  rendering that area of the panel dan-

  gerously thin. The point is: You must

  have a panel correct and level before

  The coarse file (top) has a 6-per-inch tooth count, while the fine file (bottom)

  metal finishing is a reasonable

  sports an amazing 16 teeth per inch. Most body files are in the 8-tooth-per-

  approach to achieving final contours

  inch range, ideal for most jobs. Finer files than that are for very fine finishing

  and smoothness.

  jobs and for working on aluminum panels.

  The first metal finishing tool that

  you should learn to use is the 14-inch

  body file. It is a masterpiece of func-

  tional tool design, evolved to perfec-

  tion over many years of development.

  Used correctly and in moderation, it

  can do wonderful things for you.

  Foremost among these things is filing

  off high spots and revealing low spots

  in panels. It does this by slightly cut-

  ting away surface metal above low

  spots, and leaving them visually obvi-

  ous as slight voids in an otherwise

  continuous, filed, shiny surface.

  Once low spots are located, they

  can be raised with hammers and/or

  pick hammers, and re-filed. This

  process is repeated until no low spots

  are revealed, at which point the panel

  surface is level. However, it cannot be

  repeated ad infinitum, because each

  filing cycle removes metal and makes

  a panel thinner. You need to accom-

  These are the basic file holders that I use. They offer comfortable gripping

  plish leveling in three or fewer filing

  surfaces and can be rocked, toe to heal, naturally. The flexible holder (bottom)

  applications, and that third one

  offers adjustable contour, from mild concave to mild convex, and is the most

  should be very light.

  usable holder for general work.

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  AUTOMOTIVE BODY WOR K AN D R UST R E PAI R

  M ETAL F I N I S H I NG

  Pick hammering takes skill and

  practice. Some inventions purport to

  make it easier. These pneumatic

  picks are placed against low spots

  and triggered with foot valves. True,

  you don’t have to hit an invisible spot

  from afar with them, but they are

  difficult to locate and hard to control.

  Always keep in mind that the

  object of metal finishing is to achieve

  correct contours and smooth metal

  with a minimum of material removal.

  The proper motion with a body file is forward, away from you, and slightly side-

  Beyond that, try to leave as little need

  ways. As the file is moved, your down force on it should be shifted from its front

  for body filler—plastic or metal—as is

  to its back. You should always file toward areas of lower crown.

  possible. After metal finishing, it is

  best to use little or no filler.

  Filing Done Right

  All 14-inch, flat, body files come

  in a variety of tooth counts—

  between 6 and 16 teeth per inch. The

  finer files tend to cut more smoothly,

  but to remove less metal in a stroke

  than the coarser ones, making them

  somewhat easier to use. They are

  intended for finishing work. A body

  file with 8 teeth per inch is good for

  general metal finishing work.

  Although it is possible to sharpen

  dull files several times, it is difficult to

  find file sharpening services these

  days, so it is best to try to keep your

  files sharp for as long as possible. One

  trick to accomplish this is to brush

  From the gallery of great ideas that just don’t work, I offer spring-loaded, auto-

  their teeth lightly with turpentine,

  matic Bulls-eye picks. Supposedly, you locate the target anvil over a low spot, and

  from time to time. This retards rust

  squeeze the handle. Bingo, raised metal. But most situations lack room to fit

  and lubricates the cutting action. It

  these clunky devices, and they never strike accurately enough to work.

  AUTOMOTIVE BODY WOR K AN D R UST R E PAI R

  63

  CHAPTE R 7

  The Sanding-Picking-Filing-Sanding

  Metal Finishing Routine

  The repair of two small dents in a up with a small, highly crowned body ham-

  At this point, the panel was filed with

  1948 Chrysler decklid illustrates

  mer, which reduced its size by more than

  a flat 8-tooth-per-inch body file, held in a

  the basic sanding-picking-filing-sanding

  half of its diameter. Then, we used a blunt

  slight curvature in a flexible file holder. The

  sequence that is used
in metal finishing.

  pick hammer to finish lifting its center.

  first hammering and picking operation

  This process indicates low spots, grinds

  off high spots, and ensures crown

  continuity in panels. It is also used to

  raise and repair small dents.

  The first step was to disc sand the

  paint off the panel, in the area of the two

  small dents that are the subjects of this

  repair. Since the rest of the panel was

  undamaged, and because our plan called

  for chemically stripping the panel after the

  dents were repaired, we disc sanded it

  only in an area that included the two

  spots. This would allow us to check crown

  continuity in that area, after we made nec-

  Sanding the paint off this

  1

  essary repairs.

  decklid revealed the extent

  The smaller dent was driven

  2

  The sanded area revealed the extent

  of the two medium-sized dents that

  up with a blunt pick to raise

  of each dent. It was about what we

  were the reason for the repair. Both

  its deepest area and, at the same

  expected, and well within the range of

  were perfect candidates for

  time, to slightly raise the entire

  what it is possible to repair by lifting up

  hammering up from the other side,

  area around it. Picking has to be

  and filing metal. Our first step was to pick

  and metal finishing, because both

  done with the intent to completely

  up the smaller spot with a fairly blunt pick

  offered good access for that

  level entire damage spots.

  hammer. The larger spot was first driven

  procedure.

  We used a dolly that wrapped

  4

  around two sides of the dent

  to back up our hammering. This

  controlled the movement of the

  panel area just adjacent to the

  The areas around and between the dents were sanded to bare

  dent. Hammering was done off-

  3

  metal, so that the repair could account for the crown in the entire

  dolly, and the dolly was shifted from

  repair area. The dent on the left is more complex than the one on the right.

  time to time around the dent.

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  AUTOMOTIVE BODY WOR K AN D R UST R E PAI R

  M ETAL F I N I S H I NG

  tends to double the life of a new or

  sharpened file, and helps you achieve

  the proper smooth-gliding motion.

  Body files are held in file holders

  made of wood or metal. I tend to use