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49
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Loose stitches
(Balloon stitches or isolated
idling loop)
Loose stitches
(Needle thread rises.)
Irregular stitches
Clearance between the
inner hook guide and the
protruding section of
inner hook is too large.
Thread paths have been
poorly finished.
Bobbin fails to move
smoothly.
Thread is not well tightened
in the reverse feed.
Height of the feed dog is too
high.
Feed timing is excessively
advanced.
Needle thread has not
been fully pulled up.
Stroke of the thread take-
up spring is improper.
Thread paths have been
poorly finished.
Bobbin fails to move
smoothly.
Bobbin thread tension is too
low.
Bobbin has been wound
too tight or too weak.
Check the clearance.
Check the finish of the
respective thread paths.
Check the change of
bobbin thread tension.
Compare the height with
the standard value.
Check the stroke of the
thread take-up spring.
Check the finish of the
respective thread paths.
Check the change of
bobbin thread tension.
Check the state of bobbin
winding.
Refer to “(7) Adjusting the inner
hook guide”.
Finish using a fine emery paper or
buff.
Replace the bobbin or the hook.
Use the optional walking foot and
presser foot.
Refer to “(4) Height of the feed dog”.
Lower the height by 0.2 mm than the
standard value.
Retard the feed timing.
Increase the needle thread tension.
Use the optional walking foot.
(Top-devided type)
Adjust the thread take-up spring to
move to approximately 1 mm from
the initial position when hook draws
thread maximumly.
Finish with a fine emery paper or buff.
Replace the bobbin or the hook.
Increase the tension of the bobbin
thread.
Decrease or increase the tension
applied to the bobbin winder.
Troubles
Causes
Checking
Corrective measures
Adjustment of the thread take-up spring
™
Decrease the tension of the thread take-up spring and decrease the stroke of
the spring to improve irregular stitches.
3
4
Summary of Contents for LS-1340
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