Some days you cant win, Do not give up on all your machines, If a machine keeps breaking thread, it ususally is the tension, the wrong size needle, or it needs a really good cleaning. 2 days ago I was trying tofinish something on my vintage 401, it just kept jamming thread in the bobbin case, I cleaned it no help, long story short after about an hour, I realized I had put a newly wound bobbin in the machine on a NEW bobbin, guess what that bobbin does the same in another 401 that I own, so it went in the trash, and another older bobbin went in the machine and it works just like it always does.