First I agree with intoquilting, Maxi Lock thread. I have found Joann's to have thick and thin spots within the thread. Also you are not saying what thread is breaking. I have the HuskyLock 936 serger and I can use just about any thread pleasing to me. If your needle thread is breaking are you using the correct needle and size? My Husky uses Schmetz needles size 14. If I use a smaller needle I will get breakage. If the looper thread is breaking, I would suggest that they are not threaded properly.