Auto Collision Repair and Refinishing, 1st Edition Page 178 (178 of 880)

178 Section 2 Nonstructural Repairs
Edge Alignment
Edges of doors or fenders can be pushed in during an
impact. Figure 8-30 shows a fender edge that has been
pushed inward relative to the door. A slide hammer can
be used to pull out the fender edge. An L-shaped attach-
ment is placed along the edge of the fender. Tapping
with the slide hammer, as shown in Figure 8-31, will
raise the edge of the fender so it is flush with the door.
Note that there is no buckle to remove in this example.
The door in Figure 8-32 has been pushed in and has
buckled. The edge of the door consists of three layers of
metal: the inner structure, the inner hem flange, and the
outer hem flange. Therefore, the edge of the door can
be quite stiff when buckles form. To remove the damage,
the edge should be raised as the buckle is worked. An
L-shaped attachment is placed on the damaged edge.
As one technician uses the slide hammer to remove the
damage, another technician taps on the buckle.
This task can be accomplished by one technician.
Instead of slide hammering, the technician can pull on
the shaft of the slide hammer while tapping the buckle.
Another method is shown in Figure 8-33. In this case,
the door must be removed. Locking pliers are used to
align the edge of the door. Pulling up on the locking
pliers straightens the edge of the door. The hammer
is used to tap on the buckle. The low area behind the
buckle can be raised with draw pins.
Shrinking
Shrinking reduces the surface area of stretched g
metal. Shrinking can also remove false stretch. One way
to reduce the stretched metal’s surface area is to apply
heat. Heat, even the small amount generated by a draw
pin welder or grinder, will cause the stretched metal
Figure 8-30. This fender was driven back by a front
impact. Opening the driver’s door caused damage to
the fender.
L-shaped attachment
Slide hammer
Figure 8-31. When using a slide hammer to move a
fender edge, line up the hook at the body line.
Figure 8-32. The edge of this door has been pushed in
and has buckled.

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178 Section 2 Nonstructural Repairs
Edge Alignment
Edges of doors or fenders can be pushed in during an
impact. Figure 8-30 shows a fender edge that has been
pushed inward relative to the door. A slide hammer can
be used to pull out the fender edge. An L-shaped attach-
ment is placed along the edge of the fender. Tapping
with the slide hammer, as shown in Figure 8-31, will
raise the edge of the fender so it is flush with the door.
Note that there is no buckle to remove in this example.
The door in Figure 8-32 has been pushed in and has
buckled. The edge of the door consists of three layers of
metal: the inner structure, the inner hem flange, and the
outer hem flange. Therefore, the edge of the door can
be quite stiff when buckles form. To remove the damage,
the edge should be raised as the buckle is worked. An
L-shaped attachment is placed on the damaged edge.
As one technician uses the slide hammer to remove the
damage, another technician taps on the buckle.
This task can be accomplished by one technician.
Instead of slide hammering, the technician can pull on
the shaft of the slide hammer while tapping the buckle.
Another method is shown in Figure 8-33. In this case,
the door must be removed. Locking pliers are used to
align the edge of the door. Pulling up on the locking
pliers straightens the edge of the door. The hammer
is used to tap on the buckle. The low area behind the
buckle can be raised with draw pins.
Shrinking
Shrinking reduces the surface area of stretched g
metal. Shrinking can also remove false stretch. One way
to reduce the stretched metal’s surface area is to apply
heat. Heat, even the small amount generated by a draw
pin welder or grinder, will cause the stretched metal
Figure 8-30. This fender was driven back by a front
impact. Opening the driver’s door caused damage to
the fender.
L-shaped attachment
Slide hammer
Figure 8-31. When using a slide hammer to move a
fender edge, line up the hook at the body line.
Figure 8-32. The edge of this door has been pushed in
and has buckled.

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177
Chapter 8 Nonstructural Panel Repair
with a slide hammer or a T-puller. This method is fast
and effective. However, it is easy to pull the metal too
far, creating a high spot. The high spot will be work hard-
ened and difficult to lower.
If the draw pin welder’s trigger is held down too
long, the pin will be welded deep into the metal. This
may make the pin weld so strong and the surrounding
metal so weak that when the pin is pulled, the metal
surrounding the weld will break. When this occurs, the
hole must be filled. A MIG welder can be used to fill the
hole. After filling, the built-up weld is then ground flush.
Another way to fill the hole is to use waterproof filler. The
filler can be applied to the low area, filling the hole from
the outside of the panel. The filler can also be applied
from the back side of the panel. If the hole is accessible
from the back side of the panel, remove the paint from
the back of the panel. Then apply filler to the back side
to bridge the hole. With either filler method, the back
side of the repair should be sprayed with epoxy primer
and rust proofing.
If a crease must be raised, several draw pins can
be welded close together along the crease. A gang
clamp can then be used to grab onto the pins, as shown
in Figure 8-28. The clamp can be pulled with a slide
hammer or a come-along. After the damage has been
raised, the pins are removed by clipping them with
side cutters and then grinding off the remaining heads.
Instead of pins, washers can be welded to the panel and
then pulled. W-shaped wire can also be welded onto a
panel. The W-shaped wire can be welded to a body line
or a crease. The wire is then raised with a claw handle.
See Figure 8-29. For greater pulling power, a 10-pound
slide hammer can be attached to the claw handle.
A damaged body line can be raised with a body
chisel. This requires access to the back of the panel.
The chisel face, if sharp, should be covered with
masking tape. This will prevent it from cutting into the
metal. To raise the body line, simply find the lowest
point, place the chisel on it, and hit the chisel with a ball
peen hammer. A body line is a strong area. A damaged
body line is even stronger. Light blows will probably not
move the body line enough to make a difference. Hard
blows are generally needed to move a damaged body
line. As you move the body line, check the progress on
the outside of the panel. If arrowheads are present in
the metal above and below the body line, they can be
released once the body line has been roughed out.
Draw pins
Figure 8-27. Draw pins are welded to this panel to
raise a low area.
Clamp
Figure 8-28. Several draw pins can be raised at one
time with this clamp.
W-shaped wire
Hook-type puller
Figure 8-29. W-shaped wire can be welded in a
gouge. The wire is then pulled to raise the damage.

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179
Chapter 8 Nonstructural Panel Repair
grains to thicken. The thickening causes a reduction in
surface area, thereby eliminating the stretch.
The amount of metal shrinkage that occurs depends
on the size of the heated area and the heating tempera-
ture. The heating process must be carefully controlled.
Stretch damage most commonly occurs on low-crown
panels. Uncontrolled use of heat on a low-crown panel
will cause warp damage. Warp damage is a group of
high and low areas in a panel. Warp damage is difficult
to remove, if not impossible. Always use the minimum
amount of heat required when shrinking.
One heat shrinking technique commonly used to
eliminate false stretch involves the use of a draw pin
welder and a shrinking tip. If a shrinking tip is not avail-
able, simply use the draw pin welder without a pin. If
hammering on a nearby body line does not cure false
stretch, heating with the draw pin welder will remove it.
Locate the false stretch and pop it in. Grind or sand off
the paint from the false stretch area.
Push the shrinking tip onto the false stretch and pull
the trigger on the draw pin welder. Keep the welder on
for about one second. The false stretch should remain
down and not pop up. If it does pop up, repeat the proce-
dure. If the false stretch is so big that pushing in on one
area causes another area to pop up, try shrinking the
metal between the two areas. Usually, a false stretch
area that has been shrunk must be filled.
You can also shrink a high spot using a draw pin
welder and the draw pin welder tip (or a shrinking tip).
Simply place the tip on the high spot and press the
trigger in for one second. Then tap the heated area twice
with a flat faced dinging hammer and immediately cool
the heated area with a wet rag. This method works well
on high spots that result from pulling draw pins above
the surrounding metal.
Another shrinking method involves the use of an
oxyacetylene torch or a butane-fueled micro torch to
remove a low spot. This procedure will require heating,
putting down the torch, and using the hammer and
dolly, all in a brief period of time. Therefore, a dinging
hammer, a flat dolly, and a wet rag should be nearby.
Be sure to locate a safe place for the hot torch before
you start. The stretched area should be stripped to bare
metal first. When using an oxyacetylene torch, use a
small tip, such as a #1 tip. Light the torch and adjust
it to a neutral flame. The hot spot of the flame should
be concentrated on the deepest part of the stretch.
The heated area must be no bigger than a dime. See
Figure 8-34. As steel heats up, its color changes from
silver to blue and then to red. The heating will cause the
grains to thicken, reducing the surface area. With less
surface area, the metal contracts, raising the low spot.
Immediately after the steel changes color from blue to
red, turn off the torch and set it down. Tap around the
heated area with the dinging hammer. If the back side of
the panel is accessible, the dolly can be used to support
the panel. Use light hammer-off-dolly blows to level
the area. Once the color has disappeared, the wet rag
can be used to cool the area. Using the wet rag to cool
the area while the metal is too hot with color can make
the metal brittle. The area that has been shrunk will be
harder than the surrounding metal. If many shrinks are
needed, shrink the most stretched area first, but do not
quench it (cool it with the wet rag). Shrinking with heat
will burn rustproofing from the back side of the panel.
Be sure to replace the rustproofing after heat shrinking.
As damaged metal is straightened, a stretched area,
originally a low area, may become raised. The area is still
stretched, but it is now high instead of low. A torch can
Figure 8-33. The first step in this repair is to align the
door edge with locking pliers. Tapping on the ridge
while pulling the pliers will move the edge.
Oxyacetylene torch
Figure 8-34. A torch is used to heat a small circle on a
stretched panel. Notice the color of the heated metal.

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Page 16Section 1 Introduction to Collision Repair click to expand contents

Page 136Section 2 Nonstructural Repairs click to expand contents

Page 302Section 3 Structural Repairs click to expand contents

Page 436Section 4 Mechanical and Electrical Repairs click to expand contents

Page 572Section 5 Refinishing click to expand contents

Page 784Section 6 Estimating and Certificaton click to expand contents

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