
TM 9-1829A, April 1944
41/100
2021-07-07
Figure 48: Flaring magnet shaft, using fixture (T-170666 with Det. 6)
b.
Install oil wick and plug:
Saturate oil wick in watch or clock oil, squeeze out excess oil, and insert wick in
hole in frame. Push in oil wick plug (hollow end out) until flush with hub of frame. Do not push in too far.
c.
Install second gear:
Apply a very light coat of No. 00 grease, O.D., to second gear teeth and insert in frame,
turning magnet slightly to mesh gears. Assemble bracket, lock washer and screw. Second gear end play should
be 0.008 inch to 0.012 inch. Adjust, if necessary, by bending second gear bracket.
d.
Install third gear, speed cup, and front jewel bracket:
Screw front jewel into bracket. Run the front jewel
through the bracket at least twice to make sure it screws freely. Place hair spring regulator in position, and
screw front jewel nut loosely on front jewel. For a good preliminary setting the head of the front jewel should
protrude about two threads above the lock nut. Place speed cup over magnet, taking care that staff locates
properly in the magnet bearing. Place small bakelite thrust washer over end of staff. Apply light coat of No.
00 grease, O.D., to teeth of third gear, and place gear in position, properly meshing with second gear and
intermediate gear. Assemble front jewel bracket to frame, being careful not to damage front jewel when
inserting speed cup staff. Fasten with two screws and lock washers. Check to see that third gear has slight
end play (0.002 inch to 0.010 inch). (A bent bracket sometimes makes this part assemble too tightly.) With
magnet shaft held up from the bottom with the thumb (to take out all end play), turn the front jewel down
lightly (fig. 49), using adjuster (T-178705), until there is no speed cup staff end play. Then back off the front
jewel one-third turn. Test speed cup staff end play; it should be 0.005 inch - 0.009 inch. Tighten jewel lock
nut. The hair spring regulator must be free to move after lock nut is tightened.
Caution: In setting speed cup
end play, all magnet shaft end play must be removed as described above or damage to the speedometer is
likely to occur when replaced on the vehicle.
Figure 49: Applying thumb pressure on magnet shaft while adjusting front jewel with special tool (T-178705)