– 52 –
Trouble
Cause
Corrective measure
1. Stitch skipping
1
The machine head has not been
properly threaded.
™
Refer to "10. Thread the machine
heads".
2
The hook has scratches.
™
Remove the scratches on the hook
point using a
fi
ne emery paper.
3
The timing between the needle and
hook is too early or too late.
™
Refer to "17. Needle-to-hook
relationship".
4
The clearance between the needle
and the hook point is too large.
™
Refer to "17. Needle-to-hook
relationship".
5
The pressure of the presser foot is
too low.
™
Tighten the pressure regulator.
6
The needle number selected is
improper.
™
Replace the needle with one which
is one count thicker.
2. Thread breakage
1
The hook has scratches.
™
Remove the scratches on the hook
point using a
fi
ne emery paper.
2
The returning force of the thread
take-up spring is insuf
fi
cient.
™
Decrease the tension and increase
the stroke of the thread take-up
spring.
3
The timing between the needle and
hook is too early or too late.
™
Refer to "17. Needle-to-hook
relationship".
4
The needle thread tension is
excessive.
™
Adjust the needle thread tension
properly.
5
The needle comes in contact with the
hook point.
™
Refer to "17. Needle-to-hook
relationship".
6
The clearance between the needle
and the hook point is too large.
™
Refer to "17. Needle-to-hook
relationship".
7
Faulty adjustment of the needle
thread take-up eyelet.
™
Refer to "21. Adjusting the thread
take-up stroke".
8
The needle number selected is
improper.
™
Replace the needle with one which
is one count thicker.
3. Loose stitches
(Isolated idling loops)
1
The thread has not been passed
through the notch of the bobbin case
tension spring.
™
Properly thread the bobbin case.
2
he thread path is poorly
fi
nished.
™
Grind it using a
fi
ne emery paper or
buff it up.
3
The bobbin does not rotate smoothly.
™
Replace the bobbin or the bobbin
case.
4
he bobbin thread tension is too high.
™
Decrease the bobbin thread
tension.
5
The bobbin thread tension is too low.
™
Increase the bobbin thread tension.
6
An untwisted synthtic thread is used.
™
Slightly lower the sewing speed.
(1,800 sti/min)
7
The needle number selected is
improper.
™
Replace the needle with one which
is one count thicker.
4. Faulty feed
(Multi-layered
parts
of the material cannot
be fed smoothly /
puckering)
1
Faulty adjustment of the longitudinal
position of the presser foot.
™
Refer to "18. Adjusting the walking
foot and the presser foot".
2
Feed dog height is not enough.
™
Refer to "14. Height of the feed
dog".
3
Feed dog height is excessive.
™
Refer to "14. Height of the feed
dog".
24. TROUBLES IN SEWING AND CORRECTIVE MEASURES