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TM 9-254
3-6.
Swaging - Continued
Section III. MECHANICAL ASSEMBLIES
3-7.
Worm and Worm Gear Mechanisms.
a.
General. The worm and worm gear principle is widely used in fire control instruments as a means of rotating
an instrument in azimuth and in elevation. This principle has been adopted as the standard for mechanical movements in
almost all rotating instruments.
(1)
Figure 3-14 illustrates a worm and worm gear mechanism using a worm ball cap, which is threaded for
adjustment to prevent lateral movement of the worm. The worm is held in mesh by a spring and plunger
arrangement on the end.
CAUTION
Worm ball caps presently in use in some instruments, are made of brass, phenolic (plastic), or
nylon. Any attempt to lap ball caps make of phenolic, or nylon will damage these items.
Figure 3-14. Worm and Worm Gear Mechanism Using the Worm Ball Cap
(2)
Figure 3-15 illustrates a typical worm and worm gear mechanism using a seat, socket, and threaded ring
to prevent lateral movement of the worm. The thread ring is used for adjustment and the worm is held
in mesh by a spring and plunger arrangement on the one end. Before proceeding with any maintenance
work in connection with this type of mechanism, all maintenance work for the wormshaft, as outlined in b
below, must be thoroughly understood.
3-12
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