OKAY, LISTEN TO ME A LITTLE BIT. I HAVE A KEN-QUILT. HAD A LITTLE TROUBLE BREAKING THREAD. I checked the bobbin over and over. GUESS WHAT The bobbin winder was winding lop-sided. High on one side and low on the other. If it gets over the top or close to the edge of the bobbin, I guarantee you will not sew good. While filling the bobbin, just use your finger and make sure it is filling level. Fixed!