Brother bas-311hn Instruction Manual page 69

Problem
Upper thread is
breaking.
Lower thread is
breaking.
Needle breaks.
Upper thread is not cut.
Lower thread is not cut.
Cause
Thread is too thick for the needle.
Needle is not installed correctly.
Thread is not threaded correctly.
Damage or burring in parts such as the
rotary hook, needle hole plate, needle
or thread path.
Needle and rotary hook timing is
incorrect.
Upper thread tension is too strong.
Thread take-up spring tension is too
strong.
Thread breaks due to heat.
Damage to the needle hole plate or
bobbin case.
Lower thread tension is too strong.
Needle is bent.
Needle is too thin.
Needle and rotary hook tip are
touching.
Needle and rotary hook timing is
incorrect.
Feed timing is too slow.
Movable knife is blunt.
Fixed knife is blunt.
Movable knife is not picking up the
upper thread.
Movable knife is not picking up the
needle thread because the last stitch is
being skipped.
Lower thread tension is too weak.
BAS-311HN, BAS-326H
Remedy
Select a thread which is suitable for the
needle.
Install the needle so that it faces
correctly.
Thread the thread correctly.
Repair the respective part by buffing it.
Alternatively, replace the part.
Adjust the timing.
Reduce the upper thread tension.
Reduce the tension of the thread
take-up spring.
Use a needle cooler unit (optional).
Reduce the sewing speed.
Repair the respective part by buffing it.
Alternatively, replace the part.
Reduce the lower thread tension.
Replace the needle.
Select a needle that is suitable for the
sewing conditions.
Adjust the driver needle guard.
Adjust the needle clearance.
Adjust the timing.
Advance the feed timing.
Replace the movable knife with a new
one.
Sharpen the fixed knife or replace it
with a new one.
Adjust the timing.
Adjust the standby position of the
movable knife.
Refer to "Skipped stitches occur".
Increase the lower thread tension.
9. TROUBLESHOOTING
Reference
P. 28
P. 22
P. 23
P. 40
P. 29
P. 39
P. 23
*
P. 28
P. 22
P. 28
P. 41
P. 41
P. 40
P. 44
P. 44
P. 40
P. 42
P. 43
P. 60
P. 28
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