METAL BODY REPAIR - OD1653 - LESSON 1/TASK 1
the above operation until the entire crease has been raised, then shrink
following the procedure as explained above.
(f) When performing a shrinking operation, exercise care to avoid
overshrinking the panel. This will cause the metal to warp and buckle both
in and out of the stretched area. However, if this condition does arise,
heat a small spot in the area where the panel is buckling, apply a dolly
block or spoon with enough pressure to hold the buckling section up, and
allow the metal to cool. Do not use the hammer or water in this instance.
In extreme cases, it may become necessary to repeat this operation in
several different places in the warped area.
(g) Aluminum shrinking follows the same general procedure as steel.
Care must be used to avoid burning through the metal at point of contact
with the flame because this metal absorbs heat much more rapidly than steel
and does not change color under heat. Care must be taken when using water
as a quenching media because there is a chance the metal will crack when
cooled too quickly. Just as soon as the metal starts to blister where the
flame contacts the metal, the flames must be removed, and hammering done
quickly with a wooden or fiber mallet.
(h) Certain rules should be observed at all times during shrinking
operations. They are:
1 Never quench a red hotspot. Wait until the metal has turned
black.
2 Never heat an area greater than that where pressure can be
applied at one time with the hammer and dolly.
3 Never use anything but an acetylene torch for heating a
stretched section.
4 Never attempt to shrink a panel until it bas been roughed out.
5 Never apply heat to a low spot for shrinking. Hammer it out,
then apply the beat.
6 If the stretched part of the surface is small, heat a smaller
spot.
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