Singer 401 – 401A Sewing Machine Service – Parts Manual
Adjustments included:
Time the rotating hook.
Set the presser foot at the correct height.
Thread clearance.
Feed timing.
Eliminate end play or binding of horizontal arm shaft.
Time the cam stack.
Stitch regulator.
Needle bar vibrating bracket.
Zero-out the machine.
Feed forked connection.
Hook driving shaft.
Take-up lever.
Setting feed.
To set the check spring.
Gear lubricant.
Wiring diagram.
Singer 401a parts diagram.
Parts list.
Much more!
Singer 401a parts diagram.
42 page complete service manual plus a 2 page parts manual with diagrams.
This is a Service Manual. If you need the sewing machine instruction manual, please visit our shop here.
Singer 401a Service Manual pdf.
401 401A service and repair manual.
Download PDF
HINTS AND CAUSES OF MACHINE TROUBLE
CHECK THESE POINTS WHEN MACHINE BREAKS NEEDLES
If needle is incorrectly located in the needle hole in the throat plate:
1. Try a new throat plate and note whether or not
there is improvement.
2. Needle or needle bar may be bent.
3. Needle seat in the needle bar may be clogged
with dirt or may have been burred through
damage.
4. Throat plate may be incorrectly seated. (Look for
point or polishing compound around periphery
of throat plate seat.)
IF NEEDLE STRIKES SEWING HOOK
1. Needle may be incorrectly seated.
May be using a large size 15 x 1 needle, in which case point will strike bobbin case.
3. Needle or needle bar may be bent.
4. Radial setting of needle bar may be incorrect for zigzag or twin needle sewing.
5. Needle clomp may be loose.
6. Hook may need re-timing.
7. Hook position may need adjusting-move away from the needle.
8. Needle guard or sewing hook may not be correctly related to the needle.
9. Hook may be damaged.
10. Arm or bed position may hove been disturbed by severe shock in transit.
11. Too much end play in hook shaft will cause needle interference.
12. Arm shaft connection belt may need re-timing. If
belt is stretched, replace.
13. Incorrect radial location of bight control device
in arm.
IF NEEDLE STRIKES PRESSER FOOT
1. Needle may be bent or incorrectly seated.
2. Presser bar may be too high or incorrectly set for proper alignment.
3. Presser foot may be incorrectly seated on presser bar.
4. Presser bar may be bent or damaged.
CHECK THESE POINTS WHEN MACHINE IS NOISY
Noisy hook.
2. End play in hook driving shaft.
3. Loose belt.
4. Feed dog striking hook.
5. loose-fitting needle bar frame.
6. Loose fit between worm on arm shaft and worm gear on cross shaft.
7. Binding in disc follower bracket.
8. End play in arm shaft.
9. End play in arm cross shaft.
10. Loose thread take-up lever.
11. Tightness in needle vibrating mechanism.
