Bobbin problems
 

This happened this past week. My Juki 600 is making an awful noise. Sounds as if the bobbin is spinning & jumping around. It sews but the bottom stitches aren't quite straight. I've cleaned quite a lot changed needles a couple times , tried different brand threads & new bobbins using different threads. Tried different dials, seems a little worse using higher numbers. Don't know what to try next. When I bought the machine I also bought extra bobbins. These are the ones I'm using. I have two machines so my first thought was maybe I had mixed up the bobbins. The bobbins look evenly threaded.

I agree with Tartan. I had a similar problem with one of my treadles.....suddenly seemed to stop giving me the usual lovely stitches. It turned out that I had accidently used a spindle bobbin that even though at a good glance looked correct , it was in fact just a couple of mm shorter than the correct one. I swapped over and the problem was solved. I hadn't even noticed until another member of the forum in the vintage forum pointed it out to me....did I feel foolish! You bet!!!

No experience with your particular machine but I agree with the others - go back to the original bobbins as well as making sure there's not some tiny speck of thread stuck somewhere. That sounds like more the culprit to me than anything else.

I don't know if your machine has a top drop in bobbin, but, with mine, sometimes the thread jumps out of that last place in the bobbin case and causes wonky stitches. I think I have threaded it correctly, but, I have to be careful the thread stays where it should. If it is a vertical load, then this wouldn't apply.

Not sure if your bobbin thread was wound too tightly. However, that was an 'Ah-ha' moment in one of my classes, was to never wind them at top speed. Then the thread will never get all jumbled up. Since then I haven't and I've never had another evil thread jam from the bobbin side! Good luck with your issue.

I bought new bobbins for my machine and they would not work at all, looked like the original. I took them back to the dealer and she said they were being made in China now and not precise as they use to be. She had a few of the original bobbins that solved the problem.

Thank you, That was my first thought. I know I'm using the correct bobbin.

Bingo, I hope. Will try re-winding a new bobbin later today. I know I did wind these at top speed. Hopefully that is the problem.

Tried winding bobbin at slower speed. My stitches are now looking normal. After sewing about 12 inches the awful noise starts again. The noise is still coming from the bobbin area. Seems like the bobbin is spinning way too fast. Any other tips I can try.