I would tend to think either you are using a too small needle for your fabric/thread, or that the needle is faulty and the groove is not big enough to accommodate the thread so it is tearing it up. The tension is usually not the problem on a bernina. It is usually the needle, thread, or drag on the item being sewn. Also if you have a bernina, you can slow down the motor so the friction is lowered especially on dense sewing items.
Last edited by RedGarnet222; 11-09-2016 at 12:33 PM.