196 Section 2 Nonstructural Repairs
Copyright Goodheart-Willcox Co., Inc.
Filling
Filling involves the use of filler to restore panel
contour once roughing out is completed. There are
two types of filler used on vehicles: body filler and lead
filler. Body filler, or plastic filler, is far more common
than lead filler. Body filler requires less skill to apply
than lead filler. When used properly, body filler is as
durable as lead filler, except that lead filler will not
crack as body filler does if a filled panel bends or
flexes. Restoration shops and a few body shops still
use lead filler.
Using Body Filler
Body filler should not be thicker than 1/8″. Low
spots deeper than 1/8″ should be raised before filling. ″
False stretch must be shrunk or eliminated. If a false
stretch is popped in and filled, the “oil can” will eventu-
ally pop out and crack the filler. Cracked filler will allow
moisture to reach the metal, causing rust.
N N N N O O O O T T T T E E E E
A A panel pa ne l that th at has h as been b ee n previously pr ev io us ly
damaged and repaired may be damaged
again. If the existing body filler is
thicker than
1/8″,
thicker th an 1 /8 it should be ground , it should be ground
out and the low area should be raised.
If the new fill area is adjacent to existing filler that is
1/8″
thick or less, the new filler can be blended into
″
the existing filler once the paint is removed from the
existing filler. See Figure 9-52.
The first step in filling is to closely examine the
repair area. The goal is to apply filler in a single appli-
cation. Therefore, high spots must be eliminated before
filling. Look for any high spots in the metal. Use a
straightedge to locate highs. If highs are found, tap
them down with a pick hammer.
Next, remove the paint from the fill area and 1″
(25.4 mm) beyond the fill area. A grinder with a 24-grit
disk may be used to remove the paint on high-crown
steel panels. Grinding will leave deep scratches in
the metal. The filler will anchor in the scratches. This
is called mechanical adhesion. Because the heat
produced by grinding can cause panel warping, use
only 80-grit sandpaper on low-crown steel panels and
all aluminum panels. The scratches created by sanding
with 80-grit sandpaper will also anchor body filler by
mechanical adhesion.
There are two acceptable surfaces that filler can be
applied over—bare metal and epoxy primer. For corro-
sion protection, some manufacturers recommend that
filler be applied over epoxy primer. If epoxy primer is
to be used, remove the paint from the area to be filled.
Mix the epoxy primer and spray on the recommended
number of coats. After the epoxy primer has cured,
it should be sanded with 320-grit sandpaper to provide
scratches for mechanical adhesion of the body filler.
Once the panel surface is prepared, mix the filler
according to the manufacturer’s recommendations.
Read the instructions on the can carefully. Mixing filler
and hardener is a critical step in panel repair. Using the
wrong amount of hardener will cause problems. The
can of filler will list the proper mixing ratio.
Always use clean mixing sticks, paddles, and
mixing boards. Dirty equipment can contaminate the
newly mixed filler. The mixing board must have a
nonabsorbent surface, such as metal or plastic. Never
use cardboard as a mixing board. One type of mixing
board is a tablet of nonabsorbent paper sheets. After
a sheet is used for mixing, it is torn off the tablet,
exposing the next clean sheet.
Before mixing filler, make sure it is uniform in
consistency. If a bluish liquid, which is the resin in the
filler, is visible inside the filler can, use a clean paint
stick to mix the resin back into the filler.
Use a clean paint stick or paddle to remove the
desired amount of filler from the can and place it on the
mixing board. Put the lid back on the filler can as soon
as possible. An open can of filler can be easily contam-
inated with the sanding dust present in the shop.
Paste-type hardener will separate inside the tube.
Knead the tube of hardener to thoroughly mix the
separated hardener. See Figure 9-53. Squeeze out
the proper amount of hardener next to the filler on the
mixing board, Figure 9-54. Use a clean paint stick or
paddle to stir the hardener and filler together. Continue
to stir until the filler is a uniform color, with no streaks of
hardener or unmixed filler. The filler is now ready to be
applied in the low area.
The curing of the mixed filler produces heat, which
can be felt on the mixing board. The curing process
Goodheart-Willcox Publisher
Figure 9-52. This panel contains body filler that was
applied during a previous repair.
Filler Primer