Originally Posted by
pseudoquilter
I can be sewing along and then hear this "clunking" noise to find a large clump of thread is left on the underside of my fabric from the bobbin.
What can be causing this, I have re-inserted the bobbin many times.
Rethread your machine. Install a new needle. Remove the sole plate. Remove the bobbin. Clean out debris and then oil the bobbin race. This should solve your problem.