Could it be a bad batch of needles? Sometimes they have a burr in the eye and it will shred and break the thread. Is the tension correct? Did you thread the machine with the foot in the UP position so that the thread "seats" properly between the tension disks? Are you using the same thread in the bobbin? Are you moving the piece too fast? Is your machine clean? I actually changed my needle to a size 16 denim needle when my thread was breaking. Hope you can get this resolved, Good Luck!!