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12. TROUBLESHOOTING
79
BAS-311H
Problem Cause Remedy
Reference
Thread is too thick for the needle.
Select a thread which is suitable for the
needle.
P. 26
Needle is not installed correctly.
Install the needle so that it faces
correctly.
P. 22
Thread is not threaded correctly. Thread the thread correctly.
P. 22
Damage or burring in parts such as the
rotary hook, needle hole plate, needle
or thread path.
Repair the respective part by buffing it.
Alternatively, replace the part.
Needle and rotary hook timing is
incorrect.
Adjust the timing. P. 59
Upper thread tension is too strong. Reduce the upper thread tension. P. 26
Thread take-up spring tension is too
strong.
Reduce the tension of the thread
take-up spring.
P. 58
Upper thread is
breaking.
Thread breaks due to heat.
Use a needle cooler unit (optional).
Reduce the sewing speed.
P. 22
P. 31
Damage to the needle hole plate or
bobbin case.
Repair the respective part by buffing it.
Alternatively, replace the part.
Lower thread is
breaking.
Lower thread tension is too strong. Reduce the lower thread tension.
P. 26
Needle is bent. Replace the needle. P. 22
Needle is too thin.
Select a needle that is suitable for the
sewing conditions.
P. 26
Adjust the driver needle guard. P. 59
Needle and rotary hook tip are
touching.
Adjust the needle clearance. P. 60
Needle and rotary hook timing is
incorrect.
Adjust the timing. P. 59
Needle breaks.
Feed timing is too slow. Advance the feed timing.
Movable knife is blunt.
Replace the movable knife with a new
one.
P. 61
P. 63
Fixed knife is blunt.
Sharpen the fixed knife or replace it
with a new one.
P. 63
Adjust the timing. P. 59
Movable knife is not picking up the
upper thread.
Adjust the standby position of the
movable knife.
P. 61
Upper thread is not cut.
Movable knife is not picking up the
needle thread because the last stitch is
being skipped.
Refer to "Skipped stitches occur". P. 78
Lower thread is not cut.
Lower thread tension is too weak. Increase the lower thread tension.
P. 26
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