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TM 9-254
3-9.
Helical Inserts - Continued
(3)
Push down on the extracting tool and turn counterclockwise to back the insert out of the hole.
(4)
Discard the insert. Never reuse an insert.
3-10.
Removal of Setscrews.
a.
General. The securing of mechanical components is frequently accomplished by the use of setscrews.
Disassembly of components without removing these setscrews is probably the greatest cause of damage to fire control
instruments during the inspection or repair process. Many setscrews are covered with sealing compound and paint.
Some setscrews may be installed with setscrews on top of setscrews to lock them in place. Perform an inspection of the
instrument before disassembly is attempted.
b.
Removal of Ordinary Setscrews (Undamaged). Examine the instrument and components for the presence of
setscrews. The technical manual for the instrument must be reviewed if there is any doubt concerning the presence of
setscrews. When the setscrew has been located, remove paint and sealing compound with a scriber or jewelers’
screwdriver. When the head of the screw can be seen, insert a screwdriver or Allen wrench of the proper size and remove
the screw.
c.
Precautions. If the screw will not back out when normal pressure is applied with the screwdriver or allen
wrench, do not force it. It may have been sealed in position with shellac or another fixing agent. If so, apply a few drops
of-alcohol to the screwhead and allow it to soak for a few minutes. Again insert the screwdriver or hex key wrench and
exert a slight back and forth pressure. It may be necessary to apply heat to the area around the setscrew to loosen the
sealing compound in order to remove the setscrew.
d.
Removal of Damaged Setscrews. If the slot of a setscrew below the surface is damaged, the best method is
to drill out the screw and retap the hole.
(1)
Select a tap drill of the size for the setscrew which will be used as a replacement.
(2)
Position the part to be drilled securely on the drill press with the drill centered on the setscrew, and drill
out the setscrew.
(3)
If the setscrew is not too small, it may be possible to remove it with a screw extractor (fig. 3-30).
(4)
Another method of removing setscrews is by using an insert extractor tool of the same size that will fit
the screw opening, as shown in figure 3-29.
(5)
If the setscrew is above surface, it may be possible to slot it sufficiently with a small file or hacksaw
blade (fig. 3-31).
(6)
A setscrew that can be turned, but which does not back out, indicates a stripped thread condition. It may
be possible to back out the setscrew if the parts held together by the setscrew can be turned enough to
put a slight stress on the setscrew. This will allow those threads still undamaged to engage and enable
the repairer to remove the setscrew.
3-29
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