And make sure you are using the right size of the needle. Check Superior Threads. The weight of the thread and the needle size need to match. I spent two and a half years claiming I had a bad sewing machine because my size 70 needle wouldn't sew 40 wt. Mettler thread. Finally the dealer put a 100 needle in my machine and it sewed perfect! I had complained here on the board forever about it and to my LQS owner and the dealer's wife and no one had an answer. Needle and thread must match!