METAL BODY REPAIR - OD1653 - LESSON 2/TASK 1
into the crack and left to set for approximately two or three minutes. A
slight pressure downward is applied, separating the two pieces of glass.
(4) In the hot wire method, a coil of wire 1/4 inch in diameter and 72
inches long (the wire is 1/16 inch in diameter) is heated electrically. It
is laid along the crack and covered with notched asbestos and lead weights.
One lead from the 110 volt circuit switch is permanently connected to one
end of the wire. The other lead is attached by a clip to a selected point
on the wire and the switch turned on, heating the wire to a bright red. The
heated plastic softens and the waste glass drops from its own weight. Waste
pieces less than an inch wide may have to be removed with glass pliers.
(5) Common difficulties in the hot wire method are: bubbling in the
plastic, caused by too hot a wire or too long a heating time; separation of
glass sheets along the edge of the cut, caused by stretching the plastic
excessively; and chipping along the cut, caused by bending the waste strip
up and down, rather than pulling it straight out.
g. Glass Grinding and Finishing. The grinding machine is equipped with a
chute which is set so the silicon carbide abrasives flowing onto the
roughing wheel will hit the wheel at the edge of the recess. Place a small
quantity of silicon carbide grains in the chute and saturate them with
water. Then let a continuous trickle of water run onto the grains to carry
a sufficient amount of grains onto the face of the wheel. The corners of
the glass should not be cut too close to the outline of the pattern. A more
accurate fit can be made by using the grinding wheel or belt edger on curved
surfaces.
h. Grinding. The silicon carbide abrasive grains do the cutting (grinding)
and can be reused. New silicon carbide should be added at the ratio of
about two pounds to each 1000 inches of glass beveled. Before reusing
carbide or mixing with new carbide, it is advisable to wash the old carbide
to remove all foreign matter. This foreign matter should then be strained
through ordinary window screen to remove any large chips of glass.
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