Brother BAS-343E Instruction Manual page 62

Problem
Upper thread breaks.
Lower thread breaks.
Skipped stitches
Needle breaks.
Cause
Upper thread tension
is too strong.
Needle is installed
incorrectly.
Thread is too thick for
the needle.
Thread take-up spring
tension and height are
incorrect. incorrect.
Damaged or burred
rotary hook, needle
hole plate or needle.
Thread melting
(synthetic thread)
Thread path is incorrect.
Lower thread tension
is too strong.
Corners of needle hole
plate or bobbin case
are damaged.
Clearance between
needle and rotary hook
tip is too great.
Incorrect needle and
rotary hook timing.
Driver is contacting
needle more than is
necessary.
Needle is bent.
Needle is installed
incorrectly.
Neelde is touching the
rotary hook.
Needle is bent.
Needle moves about.
Needle is too thin.
Check
Upper thread tension
Needle direction
Thread and needle
Thread take-up spring
tension and height
Damage or burring
Thread edge
Thread
Lower thread tension
Damage
Needle clearance
Needle bar lift amount
Clearance between
driver and needle
Bent needle
Needle direction
Needle clearance
Needle bar lift amount
Bent needle
Needle and threa
Needle and thread
BAS-343E
14. Troubleshooting
Remedy
Adjust the upper
thread tension.
Install the needle so
that the groove is
facing forward.
Use the correct thread
for the needle.
Adjust the tension and
height of the thread
take-up spring.
File smooth or replace
the affected part.
Use a thread cooling
device.
Pass the thread
correctly along the
thread path.
Adjust the lower thread
tension. amount.
File smooth or replace
the affected part.
Adjust the needle
clearance. the affected
Adjust the needle bar
lift amount.
Adjust the driver
needle guard.
Replace the needle.
Install the needle so
that the groove is
facing forward.tube.
Adjust the needle
clearance. the groove
Adjust the needle bar
lift amount.
Replace the needle.
Select the correct needle
for the sewing conditions.
Reduce the sewing
Use the correct needle
for the material.
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