I've had problems with breaking and it gets very frustrating. I found that the spool and bobbin thread have to be the same. Or near close. I have been using up thread that was my Aunt and Mother's after they passed away. Not all the spools are the same weight. The machines get fussy at times. Also, the needle and weight of material makes a difference. I remember using my mother's Singer she won at the Chicago World's Fair in 1936 and it wasn't nearly as fussy as the new ones.