From what I have been taught -- if your thread is tangled on the bottom, it is a top thread(ing) problem. Be really sure you are threading it the right way. It could be a small thing. Consult the book about threading. If you don't have the book that goes with the machine, try Google. So sorry you are going through this. I had to give up a NEW machine after having it in the service department several times, because of a top thread issue. I know how you can HATE it.