METAL BODY REPAIR - OD1653 - LESSON 1/TASK 1
handle forces oil through the hose to the ram, causing the plunger to travel
outward under pressure. To release the pressure, turn the release valve on
the side of the pump to the left.
d.
Hammer Finishing.
When a fender or body panel is formed, the shape of the die is transferred
to the sheet metal. Later, if the panel becomes bent, creases in the panel
tend to hold it out of shape. Nevertheless, most stresses transferred to
the metal when it was formed on the body are still in the panel. When the
stress of the crease is relieved, the panel will return to its original
shape by itself. Since the metal will try to return to its original contour
of its own accord, it must be determined what is preventing it from
returning. Usually, it will be found that a crease has been formed by
impact. This crease may exist in the panel, or it may be found that a
crease in the inner construction is preventing the panel from returning to
its original contour. If the metal is hammered excessively, it will become
stretched. For this reason, it is important that each job be approached
with the idea of relieving the strain that is holding the damaged area out
of position. Light hammer blows will not displace the metal as much as
heavy blows. Several well placed light blows are more effective than one or
two hard blows. Each well directed blow of exactly the right force is an
effort toward permitting the metal to attain its original contour. Each
misplaced blow, or a blow harder than required, may create additional damage
which must be corrected.
(1) Direct Hammering.
(a) Small pimples may be removed by direct hammering. Figure 25 and
26 (on the following page) show how the dolly block is held for this
operation, as well as the relationship of the hammer to the dolly.
(b) Before using the dolly and hammer together, it will be necessary
to clean the underside of that portion of the fender on which work will be
performed. Body panels and some fenders may be covered with sounddeadening
material (undercoat) that must be removed prior to dinging. Deadening
material may be pads or mats of a felt material glued in place, or heavy,
tarlike, black material
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