Bobbin Winding tips from a repairman
When winding the bobbin with new thread, just let the bobbin turn about 5 times and stop and snip off the thread that comes out of the top hole; then continue winding it. I wind it at a medium speed.
Also, don't fill your bobbin out to the edge of the bobbin. Stop when your thread is more than 1/8th of an inch from the edge of the bobbin.
Hope this helps,
Annette in Fl.