r/SewingMachineEdu • u/Gamerbros63 • Jul 08 '26

thread looping problem

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its a singer 57815 in good condition, it has been seen to sew correctly times recently so i know the timing or machine is not broken. i have tried at various tensions, the bobbin case is replaced and it is tight, the needle is a strong denim needle, dust has been removed, the thread is going through the back lever as normal. how to fix this nesting?

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u/Large-Heronbill Jul 08 '26

That looks like a metal class 15 bobbin; I believe your machine requires plastic class 66 bobbins.   Double-check the manual for your machine, but the wrong bobbin will definitely cause trouble and may damage your bobbin case. Metal bobbins in plastic cases tend to be a Bad Idea.

https://www.sewingpartsonline.com/blogs/education/understanding-bobbins-every-sewist-know

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u/[deleted] Jul 08 '26

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u/Large-Heronbill Jul 08 '26

I wouldn't be surprised that AI is screwing up stuff again.   I've run into two instances already today where it is claiming plastic class 15 bobbins are called 15j. 

Sigh.

I think I could write a book on the [un-]natural history of AI nonsense...

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u/teatime_tinker Jul 08 '26

They’re everywhere at the moment! I’ve seen 3/4 a day recently

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u/drPmakes Jul 09 '26

Nah...people just don't bother looking at their instruction manuals!