195
Chapter 8 Nonstructural Panel Repair
When performing shrinking, leveling, or raising opera-
tions on an aluminum panel, the hammer blows must be
softer than those used on steel. Tap lightly. The faces of
hammers and dollies used for aluminum repair must be free
from nicks and gouges. Any irregularities on the faces of
the straightening tools will be transferred to the aluminum.
Some technicians use plastic- or rawhide-faced hammers
to straighten aluminum. Most body fillers used on steel can
also be used on aluminum. The aluminum panel should be
coated with epoxy primer before applying the filler.
Summary
Displaced metal is undamaged but held out of
position by the arrowhead buckles.
The grains in the metal are too small to be seen, but
their arrangement determines the shape of the metal.
A force greater than the yield point will rearrange
the grain set, causing buckles and changing the
shape of the panel.
A stretch means that the grains have been thinned,
flattened, and elongated.
An upset means that the grains have been
shortened, thickened, and bunched together.
Only after you carefully examine and analyze the
damage will you be able to decide if the damaged
part should be repaired or replaced.
Easily replaced, low-cost panels, such as fenders
and door skins, are often replaced if they have
more than minor damage.
To repair panel damage caused by longitudinal
force, the panel’s length must be restored.
To repair damage caused by lateral force, not only
must the length be restored but the surface area
may also have to be changed.
Before you can begin the repair of a damaged
panel, various components must be removed from
the vehicle to allow access to the damage.
Roughing out restores the damaged panel to its
approximate contour, and finishing completes the
repair by restoring the exact contour of the panel.
When metal is upset, its surface area is reduced
and its thickness is increased. Stretching restores
the metal to its correct dimensions.
A false stretch is a bulge that pops in when
pressed and out when released.
Shrinking reduces the surface area of stretched metal.
Uncontrolled use of heat on a low-crown panel will
cause warp damage.
Kinking involves the use of a shrinking hammer
(serrated-faced hammer) or a sharp pick hammer
to reduce the surface area by gathering the metal
together.
Chasing the dent occurs because the low-crown
metal is floppy and is easily pushed in.
Picking raises small lows and lowers small highs.
Filing is used to identify high areas and low areas.
In a one-sided repair, only the outside of the panel
is worked. This type of repair is performed when
the damaged panel is boxed or if accessing the
back side of the panel is difficult.
In a two-sided repair, both sides of the panel are
worked. Access to the back side of the panel is
required in a two-sided repair.
Metal finishing is the continuation of the pick and file
process started during roughing. If metal finishing is
done correctly, no filler will be used in the repair.
Filling involves the use of filler to restore panel
contour once roughing out is completed.
When performing shrinking, leveling, or raising
operations on an aluminum panel, the hammer
blows must be softer than those used on steel.
Review Questions
Please do not write in this textbook. Place your
answers on a separate sheet of paper.
1. The damage repair sequence involves analyzing
the damage, planning the repair, accessing the
damage, , and finishing.
2. A bend of reflected light on a panel indicates a(n)
in the panel’s surface.
3. A straightedge can be used to locate dents in
panels that are in only one direction.
4. A damaged panel is replaced if the cost of repair is
at least % of the cost of replacement.
5. will loosen the screws holding a steel wheel
opening molding in place.
6. Explain the lift reaction.
7. When pulling on a plate, the pull should be
perpendicular to the plate. True or False?
8. When using a hydraulic ram to lengthen a panel,
which should be stronger, the damage or the base?
9. Hammering on the dolly causes the metal to .
10. Explain how to heat shrink a high, stretched area.
11. A(n) is used to tighten floppy metal prior to
filling.
12. Pick and filing should be done at the beginning of
the repair sequence. True or False?
13. A damaged internal brace is replaced last. True or
False?
14. Filler can be applied over metal or
primer.
15. The correct sequence of sandpaper grits to use
when sanding a 12" (30 mm) diameter section of
filler is , , and .