181
Chapter 8 Nonstructural Panel Repair
Technicians sometimes oversand the filler. The
excessive sanding leads to undercutting, a condition
in which filler is sanded below the level of the adjacent
metal. When comparing the filler height to the height
of the adjacent metal, the technician misdiagnoses the
undercutting problem and taps down the adjacent metal
rather than refilling the low area. Undercutting should
not be confused with chasing the dent.
Picking and Filing
Picking and filing are operations performed at the
end of the roughing out process. Picking raises small g
lows and lowers small highs. Filing is used to identify g
high areas and low areas. Both sides of the panel must
be accessible for picking and filing.
A body file is flat or nearly flat. Files should be
used on flat surfaces. On a panel with single crown, the
filing should be done with the flat surfaces as shown
in Figure 8-38. On a double-crown surface, the filing
should be short so as to not cut into a crown. The file
is held at a slight angle as it is pushed away from the
technician’s body. Do not contact the metal on the return
stroke. The file bites into the high areas and passes over
the low areas. A couple of passes with the file will make
bright shiny areas in high spots. You can see file marks
on these spots. Also you can feel the high areas when
filing. The file will drag when it hits a high area.
After locating high areas, tap them down with a
pick hammer. If the pick hammer is sharp, the area
moved will be small and precise. A blunt pick hammer
can be used to lower larger areas. When the high area
has been removed, file the panel again. If the file glides
across the panel without dragging or cutting into a high
spot, look for low areas. Low areas are places that do
not have any file marks. Low areas should be brought
up from behind with a pick hammer. This process is
called blind picking. A sharp pick hammer may raise
a low spot up to a sharp point. If the sharp point is filed,
the file may cut the top off the point, leaving a hole in
the metal. To prevent this type of problem, do not raise
the low spot above the surrounding metal.
A bull’s-eye pick, Figure 8-39, can be used instead
of blind picking. A bull’s-eye pick has a sharp pick point k
that the technician controls by pulling on the handle.
Pulling on the handle causes the pick to hit inside the
bull’s eye. This is a very accurate alternative to blind
picking. Simply align the bull’s-eye over the low spot and
pull the handle. The pick will raise the low spot.
Additional filing and picking can be done to make
the panel level. Do not file an excessive amount of metal
from the panel. Doing so can make the panel too thin. If
you plan to fill the low areas, stop picking and filing once
all the high areas are level and the low areas are less
than 1/8" (3.2 mm) deep.
A grinder can be used instead of a file during finishing
operations, as shown in Figure 8-40. A grinder can be
stroked back and forth over the panel. If the grinding
disc is held flat to the surface, it will identify the high and
low areas, as a file would. A grinder will produce heat,
so only use a grinder in this way on high-crown panels.
As with a file, find and tap down the high areas and then
raise the low areas.
Roughing out Specific Types of
Damage
This section details the procedures for roughing
out specific types of damage. Roughing can be
performed as a one-sided repair or a two-sided repair.
In a one-sided repair, only the outside of the panel r r
Figure 8-38. When filing on a single crown panel, hold
the file as shown here.
Bull’s-eye pick
Figure 8-39. A bull’s-eye pick is being used to raise a
low spot on a vintage hood.