22
1. Stitch skipping
2. Thread breakage
3. Loose stitches (Isolated
idling loops)
1
The machine head has not been
properly threaded.
2
The hook has scratches.
3
The timing between the needle and
hook is too early or too late.
4
The clearance between the needle
and the hook point is too large.
5
The pressure of the presser foot is
too low.
6
The needle number selected is
improper.
1
The hook has scratches.
2
The returning force of the thread
take-up spring is insufficient.
3
The timing between the needle
and hook is too early or too late.
4
The needle thread tension is
excessive.
5
The needle comes in contact with
the hook point.
6
The clearance between the needle
and the hook point is too large.
1
The thread has not been passed
through the notch of the bobbin
case tension spring.
2
The thread path is poorly finished.
3
The bobbin does not rotate smoothly.
4
The bobbin thread tension is too high.
5
The bobbin thread tension is too low.
6
An untwisted synthtic thread is
used.
7
Selection of needle size
™
Refer to "10. Threading the machine
heads".
™
Remove the scratches on the hook
point using a fine emery paper.
™
R e f e r t o " 1 7 . N e e d l e - t o - h o o k
relationship".
™
R e f e r t o " 1 7 . N e e d l e - t o - h o o k
relationship".
™
Tighten the pressure regulator.
™
Replace the needle with one which is
one count thicker.
™
Remove the scratches on the hook
point using a fine emery paper.
™
Decrease the tension and increase the
stroke of the thread take-up spring.
™
R e f e r t o " 1 7 . N e e d l e - t o - h o o k
relationship".
™
Adjust the needle thread tension
properly.
™
R e f e r t o " 1 7 . N e e d l e - t o - h o o k
relationship".
™
R e f e r t o " 1 7 . N e e d l e - t o - h o o k
relationship".
™
Properly thread the bobbin case.
™
Grind it using a fine emery paper or
buff it up.
™
Replace the bobbin or the bobbin case.
™
Decrease the bobbin thread tension.
™
Increase the bobbin thread tension.
™
Slightly lower the sewing speed.
(1,800 rpm)
™
Replace with a needle which is thicker
by one.
Trouble
Cause
Corrective measure
