I just thought of another problem I had with bobbin thread breaking. I bought a 15-91 that didn't have a cord so I didn't get a chance to try out the machine. I figured I could get a cord and still not spend much since it was an auction, I bid $10 and got it. Anyway, when the cord came, I threaded it up and started sewing. It would stitch a few stitches and break the thread. I opened up the slide plate and watched as the thread looped around the case. The little finger piece that you grab to remove the bobbin case was bent a little. The thread was catching on that finger piece and getting stuck..... then the thread would break. I thought, Oh no..... bobbin cases are expensive. But the case for the 15-91 was about $5.00.... yeah! Now, that machine sews like a dream..... just needed a new cord and a new case. I have a total of $25-30 in her... not bad.