TM 9-1829A, April 1944
52/100
2021-07-07
g.
Replace hair spring (fig. 70):
Place speed cup on anvil of hair spring assembly fixture (T-29 Det. 5). Be sure
tiny thrust washer is over end of speed cup staff, and place front jewel bracket over end of staff. Place hair
spring over end of staff with loose end of spring pointing counterclockwise. Using female punch (T-29 Det.
2) carefully drive hair spring on staff leaving about
1
/
8
inch clearance between hair spring collet and front
jewel.
Figure 70: Replacing hair spring, using assembly kit (T-29)
h.
Replace speed cup and front jewel bracket (fig. 56):
Place speed cup, front jewel bracket, and hair spring
assembly in frame. Insert rear jewel bracket, and fasten in place. Then fasten upper jewel bracket in place.
Test speed cup for free turning and end play.
i.
Replace hair spring pin and aline hair spring: Insert end of hair spring in hair spring regulator
(counterclockwise direction) with end of spring protruding through slot about
1
/
8
inch. Using long-nosed
pliers, place one jaw of pliers on large end of pin and other jaw on hair spring regulator and squeeze pin
tightly in position (with small end of pin pointing clockwise) (fig. 57). Using adjuster (T-51742) turn hair
spring collet on staff (fig. 71) until speed cup stop rests against rear jewel bracket and so that hair spring tends
to pull speed cup in counterclockwise direction. Using tweezers, carefully line up hair spring so that coils are
equally spaced and do not touch one another when speed cup is in any position.