Help with thread wrapping around bobbin case.

[Wizcrafts]

12 minutes ago, cynthiab said:

Thank you kgg. I checked it and it is seated properly. 

I have experimented with different threads. A 136 on top and a 92 in the bobbin case. It was a tiny bit better However, I'm still getting the threads wrapped around under the top edge of the bobbin case periodically.  The stopping and turning seemed to be the culprit.  But not always. I have followed what wizcafts suggested on the needle position before turning. That helped a bit too. However it's still hit or miss if I can sew on a peice of webbing to leather without it jamming up in the bobbin area or shreadding the thread. Ugh!

By the way, I did retime the needle and made sure the gap between hook and needle was correct. Didn't help...

There's only three things left that I can think of.

1. Readjust the check spring for more or less travel, or tension, or slack.
2. Check the main shaft to see if there is a lot of slop in the gears. If there is too much slop, starting and stopping with a jerk can throw off the timing.
3. Check for sharp edges along the top thread path to the needle. If there's a thread guide on the bottom of the needle bar, remove it and check it for a sharp edge. Use Emory cloth to smooth it, or replace it.

[cynthiab]

Thank you I'm on it, and will get back to you.

[Uwe]

With this type of hook, you may also experience the thread falling off and getting caught under the hook if you stop at precisely the wrong moment, turning or not. That’s what your multi-thread pictures actually looks like. 

This topic from 2016 goes into details and possible fixes:

 

 

[Michiel]

I have seen twice a machine with a slightly bend upper axis

Because of the load of the timing belt it sometimes resulted in the hook turning a little backwards when the machine stopped.

(and than happend what you describe)

this did not happen till  the old motor (with break) was replaced by  a servo motor.

the first time it took me some time to figure out wat was going on……

Edited June 9, 2024 by Michiel