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Phenomenon
① When the needle thread tension is too low.
Loose
② When the tension of the thread take-up
stitch
spring is too low.
③ When the tension of the bobbin thread is
too high.
④ When the timing of the sewing hook and
the needle is not matched.
⑤ When the thread is too thick for the needle.
⑥ When the thread slips out of the rotary
disc.
① When the bobbin thread tension is too
Irregular
stitch tight-
low.
② When the bobbin thread is not wound
ness
correctly.
③ When there is a scratch on the thread
path of the sewing hook, bobbin case,
thread take-up lever or any other parts.
① When the needle is bent.
Needle
② When the quality of the needle is not
breakage
good.
③ When the needle is not entirely inserted
into the needle bar.
④ When the needle hits the sewing hook.
⑤ The needle is too thin for the sewing
material and thread.
⑥ The needle hole in the throat plate is too
narrow.
⑦ The needle hits against the throat plate.
⑧ The needle hits against the presser
foot.
Cause
– 185 –
Corrective measures
○ Increase the needle thread tension.
○ Increase the tension of the spring.
○ Decrease the bobbin thread tension.
○ Adjust the timing correctly.
○ Use a suitable needle or thread.
○ Increase the tension of the preten-
sion disk.
○ Increase the bobbin thread ten-
sion.
○ Wind up the bobbin thread even-
ly.
○ Remove such a scratch or replace
the component.
○ Replace it with a new needle.
○ Use a needle of good quality.
○ Insert the needle into the needle
bar as far as it will go.
○ Adjust the timing and clearance
between the needle and the sew-
ing hook and also the position of
the needle guard.
○ Replace a suitable needle.
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