– 24 –
Troubles
Causes
Corrective measures
4. Loose stitches
①
Bobbin thread does not pass through
the tension spring of the inner hook.
②
Thread path has been poorly finished.
③
Bobbin fails to move smoothly.
④
Bobbin case opening lever provides
too much clearance at the bobbin.
⑤
Bobbin thread tension is too low.
⑥
Bobbin has been wound too tightly.
◦ Thread the bobbin thread correctly.
◦ Remove rough parts with a fine emery pa
-
per or buff it up.
◦ Replace the bobbin or hook with a new one.
◦ Refer to
◦ Increase the bobbin thread tension.
◦ Decrease the tension applied to the bobbin
winder.
5. Thread slips off the needle
eyelet simultaneously with
thread trimming.
①
Thread tension given by the tension
controller No. 1 is too high.
◦ Decrease the thread tension given by the
tension controller No. 1.
6. Thread slips off the needle
eyelet at the start of sew-
ing.
①
Thread tension given by the tension
controller No. 1 is too high.
②
Clamp spring has improper shape.
③
Bobbin thread tension is too low.
◦ Decrease the thread tension given by the
tension controller No. 1.
◦ Replace the clamp spring with a new one or
correct the current one.
◦ Increase the bobbin thread tension.
7. Thread is not cut sharply.
①
The blades of moving knife and count-
er knife have been improperly adjust-
ed.
②
The knives have blunt blades.
③
Bobbin thread tension is too low.
◦ Refer to
OF COUNTER KNIFE AND MOVING
KNIFE" p. 18
.
◦ Replace the moving knife and counter knife
with new ones, or correct the current ones.
◦ Increase the bobbin thread tension.
8. Thread remains uncut after
thread trimming.
(Bobbin thread trimming
failure when stitch length is
comparatively short.)
①
Initial position of the moving knife has
been improperly adjusted.
②
Bobbin thread tension is too low.
◦ Refer to the Engineer’s Manual.
◦ Increase the bobbin thread tension.
9. Thread breaks at the start
of sewing after thread trim-
ming.
①
The needle thread is caught in the
hook.
◦ Shorten the length of thread remaining on
the needle after thread trimming.
Refer to
.
10. Length of thread remain-
ing on the material after
thread trimming is too
long.
①
Thread trimming is carried out at a
position which is located outside the
material edge.
②
Thread trimming is performed in the
reverse feed stitching direction.
◦ Carry out thread trimming on the material.
◦ Carry out thread trimming in the forward
feed stitching direction.
◦ Change the function setting No. 158 to "1"
to change the thread trimming method to
the 1-stitch condensation thread trimming
(*1). (Refer to the Instruction Manual for the
SC-922 for how to change the setting.)
11. Thread cannot be
trimmed when thread
trimming is carried out at
a position where there is
no material.
①
Thread trimming is carried out at a
position which is located outside the
material edge.
◦ Carry out thread trimming on the material.
◦ Change the function setting No. 158 to "1"
to change the thread trimming method to
the 1-stitch condensation thread trimming
(*1). (Refer to the Instruction Manual for the
SC-922 for how to change the setting.)
*1 "1-stitch condensation thread trimming" means the thread trimming operation during which a condensation stitch is
sewn before carrying out thread trimming.
