Singer 491D, Service Manual

Page: 24 / 44

1. Insert the machine-pulley-end of the arm shaft into the arm shaft bushing
at the head of the machine arm.
2. Make certain that the needle bar crank is turned to the position shown in
Fig. 30, clearing the three wick loops in holder U3.
3. While still holding the bevel gears at J2 in mesh, with a screwdriver,
as shown in Fig. 31, push the arm shaft V3 straight through the machine
arm, thrust collar, bevel gear, and feed and feed lifting eccentric X3.
When installing the new arm shaft, make certain that every care is taken
to avoid injury to the ring and the oil seal in the arm shaft bushing
(back).
4. Replace machine pulley on the arm shaft, pushing it on until it contacts
the oil seal and with the two set screws S3 located over the two grooves
on the shaft. Then pull out machine pulley approximately 1 mm and se-
curely tighten set screws S3. (When machine pulley is correctly set in
position, the end of the arm shaft should be located approximately 1 mm
inside the outer surface of the hub of the machine pulley.)
5. Replace and tighten the arm shaft screw R3. Test the arm shaft for
freedom in rotation.
6. Move feed and feed lifting eccentric X3 toward machine pulley and securely
tighten feed timing screw M.
7. Place the first finger of one hand on one side of the arm shaft and the
first finger of the other hand on the other side of the arm shaft so that
both fingers contact the bevel gear (on vertical shaft) that mates with
the gear J2, Fig. 31. Feel for slight backlash. If there is no backlash,
loosen two set screws P3. Lightly tap bevel gear away from mating gear
until there is just a slight amount of backlash. Then securely tighten
set screws P3 in bevel gear. Re-check the backlash.
8. Turn machine pulley over toward operator until the two set screws Q3 in
the thrust collar which also serve as a balance weight are at the top.
Align and securely tighten the upper set screw Q3 (set screw which appears
immediately after the first set screw when machine pulley is rotated over
toward operator) on the timing mark provided for it on the arm shaft.
Then securely tighten the other set screw Q3.
- 20 -
REPLACEMENT (See Fig. 31)
Q3
P3 M
S3
R3
S3
X3
V3
J2
Fig. 31
HOLD GEARS IN MESH