Upper Shaft Mechanism - Brother RH-981A Service Manual

3-3. Upper shaft mechanism

1. Insert the upper shaft (1) into the arm from the right, and place the upper shaft collar (2), the needle bar gear (3),
the zigzag cam (4), the thrust washer (5), the upper shaft tension pulley assembly (6), and the timing belt on it.
* The emergency stop switch cord should be routed above the upper shaft.
2. Position the zigzag fork so that the zigzag cam (4) is between the arms.
3. Attach the ball bearing cap S (7) using the three flat screws (8).
4. Place the ball bearing (9) on the upper shaft, and secure it using the retaining ring (10).
5. Lightly press the needle bar gear (3) and the zigzag cam (4) toward the pulley so that the ball bearing (12) is
pressed between the retaining ring (11) and the upper shaft collar (2).
Tighten the set screw which comes first when the shaft is rotated in the rotation direction, against the screw flat.
6. Position the zigzag fork between the zigzag cam (4) and the thrust washer (5) so that there is no play between
them, face the screw flat to the front, and secure the upper shaft tension pulley assembly (6) by tightening the set
screw which comes first when rotated in the rotation direction, against the screw flat. Then tighten the other set
screw.
7. Temporarily tighten the pulley with its screw flat facing the front.
RH-981A
3. ASSEMBLY
3720Q
22