Brother BAS-311F-0 Instruction Manual page 77

14. TROUBLESHOOTING
Problem
Upper thread is not
trimmed.
Thread jamming.
Poor seam finish on
reverse side of material.
Incorrect thread
tightness.
70
Cause
Fixed knife is blunt.
Movable knife does not
pick up the thread.
The movable knife does not pick
up the thread because of skipped
stitches at the sewing end.
Movable knife position
is incorrect.
Sub-tension is too weak.
Thread take-up spring
tension and height are
incorrect.
Incorrect needle and
rotary hook timing.
Shuttle race thread guide
is not separating the
threads.
Shuttle race thread
guide is not separating
the threads.
Upper thread is not
properly tight.
Uneven upper thread
length.
Upper thread tension is
too weak.
Lower thread tension is
too weak.
Thread take-up spring
tension and height are
incorrect.
BAS-311F-0, 311F-L, 326F-0
Check
Fixed knife blade
Shuttle race thread
guide position
Needle bar lift amount
Skipped stitches at
sewing end
Movable knife position
Sub-tension
Thread take up spring
tension and height
Needle bar lift amount
Shuttle race thread
guide position
Shuttle race thread
guide position
Upper thread tension
Upper thread length
Upper thread tension
Lower thread tension
Thread take up spring
tension and height
Remedy
Sharpen or replace the
fixed knife.
Adjust the position of the
shuttle race thread gudie.
Adjust the needle bar lift
amount.
Refer to "Skipped
stitches occur".
Adjust the position of the
movable knife.
Turn the sub-tension nut
to adjust the tension.
Adjust the tension and
height of the thread take-
up spring.
Adjust the needle bar lift
amount.
Adjust the position of the
shuttle race thread guide.
Adjust the position of the
shuttle race thread guide.
Adjust the upper thread
tension.
Adjust the sub-tension.
Adjust the upper thread
tension.
Adjust the lower thread
tension.
Adjust the tension and
height of the thread take-
up spring.
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