TM 9-1829A, April 1944
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2021-07-07
d)
If the over-all dimensions of the core to be replaced cannot be determined, then it will be necessary
to measure the casing with which it is to be used. Ordnance standard core assemblies for both
diameter casings should be made 1
1
/
8
inches longer over-all than the distance between the casing
ferrule ends. This measurement will be exact for small core on which the ends are to be squared, but
on the large-diameter core consideration must be given to amount of core insertion in each tip, plus
the remaining tip length. Squared tip core must have a retaining collar crimped at the upper or
speedometer end. The location of this collar should be
61
/
64
inch from the underside of the tip collar
to the end of the squared core. Upper tips always have this collar formed as an integral part. The
collar keeps the core from falling into the casing and disengaging from the speedometer.
(2)
Cut new core:
After determining over-all length of old core, cut same length from new bulk core stock
of same diameter as old core. This is done by fixture (T-136374; fig. 126). Grind off any burs on end of
core stock. Note:
Never cut new core to longer length than old core. However, new core may be slightly
shorter than old core.
Figure 126: Cutting core stock, using fixture (T-136374)
(3)
Make up new core end connections:
Make up new core end connections identical to those on old core
as follows:
a)
Squaring end of inner core
(fig. 127): Using fixture (T-136374), insert proper length of core end
between proper squaring dies (refer to old core). Hold core firmly, keeping portion to be squared in
a horizontal position. Using heavy hammer, strike hard blow on fixture to start squaring operation.
Turn core
1
/
4
turn in die, and again strike fixture hard blow with hammer. Repeat these operations
until end of core is sufficiently squared.
b)
Crimping on bushing:
On inner cores where the upper end is squared (step (1) above), a bushing
(fig. 125) is used to hold squared end of core into neck of instrument. Place bushing in proper
location on end of core, Bushing is usually located at the end of the square formation, and the
measurement can be taken from the old core assembly (par. 52 a (1) d)). Using fixture (T-136374),
insert bushing between upper and lower crimping die, hold core firmly and, using heavy hammer,
strike hard blow on fixture. Remove from die and check to see that bushing is securely crimped to
inner core.