TM 55-6680-234-40
magnet charger Model 2470 or 2470-350 with
(2) Install bearing and dial (2) on dial
magnetizing fixture 1489444 to charge the
plate.
magnet assembly to full magnetic strength.
(3) Align and press jewel (6) in hole in
Discharge maximum current through the
end of front shaft (7) with high
windings of the magnet charger. Remove the
point of jewel toward bottom of
magnet assembly from the magnet charger di-
hole. Carefully press jewel to its
rectly into magnet keeper 1489036-1, being
seat. Inspect jewel as specified in
careful to avoid exposure to an open magnet-
ic circuit. Do not remove magnet assembly
(4) Install hairspring shield (10) and
from the keeper until it is inserted directly
shim (11) on front shaft (7) as fol-
from the keeper into the return path in the
lows. View shaft from rear. Place
indicator.
long arm of balance wheel in the
12 o'clock position; if hairspring was
Note. In order tO stabilize the magnet assembly
after magnetization, perform the following tempera-
removed, install hairspring on shaft
ture cycle. Immerse magnet assembly (in its keeper)
so the free end of hairspring faces in
in dry ice for two hours, then submege in boiling
the clockwise direction at the 135
water for ten minutes. Repeat this cycle a minimum of
degree position measured from 12
four times.
o'clock. Maintain these relative posi-
tions and press hairspring (12), shim
or 11) have not been demagnetized, omit the
(11), and shield (10) to seat against
procedure that follows and proceed to g be-
shoulder of shaft (7). Distinguish
low. (Demagnetization of either rotor would
hairspring (12) of front plate and
occur if it were exposed to an open magnetic
shaft assembly (figure 5) by 8 1/2
circuit or if it shorted against another magnet
turns from hairspring of rear plate
or metal surface.) If either rotor assembly
and shaft assembly (figure 7) by 9
zation, proceed as follows.
1/2 turns. Hairspring must be paral-
Use magenetreater Model 889A and coil
lel to shield; in the free or unwound
fixture HC-7010-7 to completely demagnetize
condition, hairspring must be cen-
the rotor. Then use fixture 1489072 with
tered on shaft. Outer end of hair-
magnet charger 2470 or 2470-350 to fully
spring must be so located that con-
demagnetize the rotor. Fixture 1489072 must
volutions are equally spaced when
be used to obtain the proper magnetic charge.
hairspring is wound up approximate-
Demagnetize to a field strength of 380 to
ly 150 degrees; to obtain this condi-
420 gauss. (Somewhat higher levels of mag-
tion, bend tab of hairspring plate
netization--up to 500 gauss--can be used
(16) if, and, as necessary, before
provided that the field strength of the poles
soldering hairspring in place; do not
is uniform.) Insert the rotor directly from the
bend hairspring,
magnetizing fixture into magnet Keeper
(5) Install hairspring plate (16) on rear
1489071 or immediately install it into the in-
plate (20). Install hex head screw
dicator. Do not weaken the magnetism by al-
(13) and washers (14 and 15)
lowing the rotor or its keeper to" contact other
through adjustment slot and secure
magnets or magnetic materials.
hairspring plate in the position that
g. Reassemble front plate and shaft assem-
will allow a gap of 0.020 to 0.060
bly and associated components as follows.
inch between pin (5) and long arm of
(See figure 8.)
balance wheel (8) when hairspring
(1) Align and press roll pin (5) into
is in free or unstressed condition.
hole in dial plate (4) to such a dis-
tance that its tip extends the distance
(6) A shim (18) of proper thickness
0.100 as measured from the sur-
must be selected to obtain correct
face recessed in the rear side of the
end play of shaft. Place a trial shim
dial plate (4).
(18) and shim (19) on rear end of
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