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Problem
Upper thread breaks.
Lower thread breaks.
Skipped stitches occur.
Needle breaks.
Cause
Upper thread tension
is too strong.
Needle is installed
incorrectly.
Thread is too thick for
the needle.
Thread takeup spring
tension and height are
incorrect.
Damaged or burred
rotary hook, needle
hole plate or needle
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.
Needle is striking the
button.
Needle is touching the
rotary hook.
Needle is bent.
Wayward stitches
Needle is too thin.
LK3-B448E MARK
Check
Upper thread tension
Needle direction
Thread and needle
Thread takeup spring
tension and height
Damage or burring
Lower thread tension
Damage
Needle clearance
Needle bar lift amount
Clearance between
driver and needle
Bent needle
Needle direction
Needle down setting
Needle clearance
Needle bar lift amount.
Bent needle
Needle and feed
timing
Needle and thread
II
/BA-16
18. 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
takeup spring.
File smooth or replace
the affected part.
Adjust the lower thread
tension.
File smooth or replace
the affected part.
Adjust the needle
clearance.
Adjust the needle bar lift
amount.
Adjust the driver needle
guard.
Replace the needle.
Install the needle so
that the groove is facing
forward.
Adjust so that the
needle drops down into
the hole of the button.
Adjust the needle
clearance.
Adjust the needle bar
lift amount.
Replace the needle.
Adjust the needle
down detection
position.
Use the correct needle
for the material.
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