I have done a lot of machine quilting on my Bernina using metallic threads. It also helps to lubricate the thread with what is called Sewers Aid. I always bought it at JAF. Run a thin line down one side of the spool. I also changed from using Sulky to using a metallic called YENMET. It was such a great difference that it seems a long time since I had a thread break. Keep trying different suggestions until you find what works BEST for you. Good Luck !!! :)