You know...I've been asking this question for some time...because I keep purchasing machines from auctions...then some are only good for parts. I have a collection of "parts". So...what I've learned to do, without any book to tell me and it's too confusing to look at the bobbin picture when researching the machine online....my heart uses a bobbin in any machine, if it works GREAT..if not, it goes into a box of "please find a new home" for box....problem solved!