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Trouble
Cause (1)
Cause (2)
Check and corrective measures
3. The thread tension is
inappropriate at sewing
start.
3-1) The tension of the needle
thread is too low at sew-
ing start.
1-A) The hook thread presser is inappropri-
ately mounted.
Adjust the hook thread presser in accordance with 3.-
(9)-7.
1-B) Bobbin idling causes the bobbin thread
tension at sewing start to decrease.
Adjust the hook thread presser in accordance with 3.-
(9)-7.
Adjust the tension of the idling prevention spring of the
bobbin case.
1-C) The tensions of the bobbin thread and
needle thread are too low.
Increase the tensions of the bobbin thread and needle
thread.
1-D) The presser or throat plate is inappro-
priate.
Refer to the previous item, [An inappropriate needle,
throat plate, or presser is used. Alternatively, he pres-
sure of the presser is too low].
4. The needle thread is un-
trimmed. (But the bobbin
thread is trimmed.)
4-1)
Stitch skipping at the final
stitch occurs.
1-A) The needle is inappropriately mount-
ed.
Mount a needle appropriately and make sure that the
needle is not bent.
1-B) The stroke of the thread take-up spring
is too long.
Shorten the stroke of the thread take-up spring. (5 to 7
mm)
1-C) The hook is inappropriately adjusted.
Check for stitch skipping at low sewing speed, and re-
adjust the hook timing (Hasten the timing of the hook.).
4-2) The blade portion of the
knife is blunt.
2-A) The blade portions of the moving
and counter knives are not per- feat-
ly aligned at thread trimming. (The
mounting angle, position, and blade
inclination of the counter knife are
not matched with those of the moving
knife.)
Remove the throat plate, and
manually operate the thread
trimmer to cut about three cotton
thread #50. When all the three
threads are cut evenly, no further
corrective action is required. If
not;
Sharpen the
counter knife.
Correct the tilt of
the blade tip of
the counter knife.
Correct the
position of the
counter knife.
