204 Section 2 Nonstructural Repairs
Copyright Goodheart-Willcox Co., Inc.
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.
■ Steel particles left over on grinder disks,
sandpaper, and files will contaminate bare
aluminum.
■ Do not heat an aluminum panel to more than
400 degrees F.
■ When performing shrinking, leveling, or raising
operations on an aluminum panel, the hammer
blows must be softer than those used on steel.
Activities
1. Write up a damage analysis on the nonstructural
damage of a vehicle chosen by your instructor.
2. On a vehicle chosen by your instructor, straighten a
damaged panel close to its original contour. Keep a
record of the tools and methods you used, and any
difficulties you encountered.
Review Questions
Answer the following questions using the information
provided in this chapter.
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?