METAL BODY REPAIR - OD1653 - LESSON 1/TASK 1
7 It is possible to shrink metal without quenching each spot
with water. However, the shrinking operation is much faster if each spot is
quenched with water. Less heat spots are required if the heat expansion is
drawn out by quenching, rather than by additional spots.
(3) Cold Shrinking.
(a) The shrinking dolly is formed so that two sides of it have a low
crown radius, with the two ends being concave.
(b) The hammer used is the offset crosspeen. The hammer is similar
to other hammers except that one end of the head is shaped to exactly fit
the concave contour of the shrinking dolly.
(c) After a weld has been made, it sometimes becomes necessary to
sink the weld. The concave portion of the dolly block is placed directly
underneath the weld.
A blow is then struck with the peen side of the
hammer, driving the weld down so that a valley is formed. This depression
is made the entire length of the welded joint and later filled with body
solder or filler.
(d) To cold shrink a panel, place the shrinking dolly under the high
spot and form a concave bead or valley as previously outlined in paragraphs
7e(3)(a) through (c) above. Move the dolly along slowly in a straight line
beneath the high spot and strike the outside surface with the hammer.
Do not make the bead any longer or deeper than necessary to draw the
stretched metal back to its normal contour. It may be necessary to make an
X-shaped bead. The X-shaped valley is made the same way as a single valley
except that a second one is made at right angles to the first one.
(e) When shrinking aluminum, it may be better to cold shrink instead
of hot shrink. The procedure for cold shrinking aluminum and steel are the
same.
f.
Body File.
(1) A body file is used for many things: to remove paint, smooth metal,
find low spots, remove excess solder, quickly remove aluminum, and to form
the correct contour of areas that have been built
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