2
Condition
Cause
How to Fix
Reference
3. Breaking
upper thread.
1. Initial sewing speed is too fast.
2. Thread path is incorrect.
3. Needle is bent or dull.
4. Top tension is too strong.
5. Needle size is inappropriate for
fabric.
6. Needle eye is worn.
7. Needle hole in needle plate is
worn or burred.
Start with medium speed.
Use the proper thread path.
Replace with a new needle.
Adjust top tension correctly.
Use appropriate needle for fabric and
thread in use.
Change the needle.
Repair the hole or replace the needle
plate.
P. 17
4. Breaking
bobbin thread.
1. Bobbin holder is incorrectly
threaded.
2. Too much thread is wound on the
bobbin,
3. Lint is stuck inside the bobbin
holder.
4. Thread quality is too low.
5. Thread is jamming around the
bobbin holder.
Set the bobbin thread correctly.
Adjust the position of bobbin winder
stopper.
Clean the bobbin holder.
Change to a high quality sewing thread.
Clear out the jamming thread.
5. Needle
breakes
1. Needle is hitting the needle plate.
2. Needle is bent or worn.
3. Needle is hitting the hook.
4. The fabric moves while the needle
is piercing it, or the needle zigzags
while in fabric.
5. Fabric is being pulled too strongly
while sewing.
See mechanical adjustment " Needle
drop position ".
Change the needle.
See mechanical adjustment " Clearance
between needle and hook ".
See mechanical adjustment " Needle
swing timing ".
Guide the fabric gently while sewing.
P. 10
P. 13
P. 16
Summary of Contents for NH40
Page 1: ...SERVICE MANUAL MODEL NH40...
