Originally Posted by
Tartan
The thread might be doubling back on itself and snapping in the tension disc? Try having it feed so it doesn't wind or circle so the doubling back won't happen. Maybe a cup behind the machine with a couple of new thread guides taped to the machine? I have taped a safety pin upside down for an extra thread guide and threaded it through the round hole at the end but a paper clip will work too.
You have suggested exactly what I was thinking. If this was happening to me, and it has, I would sew again and watch the spool of thread carefully. When I have had sudden stops & then breaks with the upper thread, it was because the thread caught on a rough spot on the spool and hung up, then popped/broke. I have a Brother machine that will only let you put the spool on sideways. Any nick in the spool where the thread spools off will create a problem for me. I solved the problem by using a separate thread stand and running the thread around the bobbin winder guide to the take up lever. When I use the 1100 meter small cones, too much thread spools off and knots up...causes the same breakage.