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Trouble
Cause (1)
Cause (2)
Check and corrective measures
2. The needle thread slips
off the needle at the sew-
ing start.
2-1) The length of the needle
thread passing through
the needle varies after
thread trimming.
1-A) Too high 1st thread tension due to
delayed thread trimming timing causes
the thread to be cut before engage-
ment between the moving and counter
knives. (midway cut)
Turn off the power, push the hook thread presser into
the bobbin case by hand when the needle reaches the
lowest point, trim the needle while turning the hand
wheel, and stop the hand wheel when the thread take-
up lever comes to the upper dead point.
If the length of the needle thread passing through the needle
at this moment is 10 mm or more shorter than that of the
pedal operation, hasten the timing of thread trimming or de-
crease the 1st thread tension because this is a midway cut.
2-2) The cause and measures
are the same as those for
the item, "1. Skipping of
one or more stitches oc-
curs at the start of sewing".
2-A) The thread take-up picker does not
enter the bobbin case sufficiently,
causing the needle thread to come off
the thread take-up picker from time to
time.
Adjust the hook thread presser in accordance.
2-B) The blade of the counter knife has been
sharpened excessively, and thread is
trimmed only by the counter knife.
Re-sharpen the blade of the knife in accordance.
2-C) The knife thread guide, moving knife,
or hook has a flaw.
Remove the scratches or burrs, or replace the defec-
tive component.
2-D) The needle is too thick.
Change the needle.
2-3) The needle thread slips
off the needle immediate-
ly after thread trimming.
3-A) Too early cam timing or too late hook
timing causes the moving knife to cut
the needle thread to hold 3 threads
before thread separation.
Slipping of the needle thread from the needle immedi-
ately after thread trimming results from cutting the nee-
dle thread passing though the needle due to defective
thread spreading by the moving knife. In such a case,
Thread chips of 40 mm level exist under the throat
plate or on the underside cover. In this case, delay the
timing of the thread trimming cam.
2-4) Knot tying between the
needle and bobbin threads
is not easy at sewing start.
4-A) The sewing speed at sewing start is
too fast to knot the needle and bobbin
threads together.
Conduct 1 or 2 stitches of soft-start (800 sti/min) at the
sewing start.
2-5) Improper clearance of
picker
5-A) The picker is too strongly functioning
and it disturbs idling that is needed for
the bobbin.
Adjust the picker alignment to a weaker level.
