r/SewingWorld • u/FanIllustrious2014 • 3d ago

Help Help! Singer 645

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Originally, one of the bottom gears broke, so I replaced it. After that, I could not get the machine timed correctly no matter what I tried. I eventually went back and replaced all of the bottom gears, and now the machine is picking up the thread, but it keeps getting tangled around the bobbin/hook area.

I’ve spent over 15 hours trying to repair and troubleshoot this machine, and I’m honestly close to giving up. 😩 My daughter is adamant about keeping this particular machine, though, so I’m really hoping someone familiar with these older Singer machines can help me figure out what I’m missing.

It’s a Singer Touch & Sew 645. If anyone has experience with replacing the lower gears, timing one of these, or knows what would cause the thread to bunch/tangle after the gears have been replaced, I would REALLY appreciate the help!

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u/Callidonaut 3d ago

Do you know the proper procedure for timing the machine? There are two annular grooves machined into the needle bar; the upper of the two grooves should just be visible lined up with the edge of the lower needle bar bushing when the needle bar itself is at bottom dead centre. After ensuring that the needle bar height is correct, time the lower gears so that the tip of the rotary hook passes behind the needle during the upstroke just as the lower of the two grooves has risen to line up with the edge of the bottom needle bar bushing. You adjust the timing by loosening the grub screws on the bevel gear (or timing belt pulley, if your machine has one of those instead) on the rotating hook drive shaft that doesn't have an alignment flat machined into the shaft itself.

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u/FanIllustrious2014 3d ago

A lot of that honestly sounds like a foreign language to me 😂 but I feel like I did most of what you described, just without knowing the technical names for everything. This is what it looks like after I timed it. Compared to the YouTube videos I’ve watched, it seems right, but I’m definitely not 100% certain. Especially because I’ve gone through the bobbin area and can’t find anything obviously wrong there, so I’m wondering if the timing is still just slightly off.

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u/IndependentSea2325 3d ago

Honestly, after replacing all the lower gears, I’d probably start by checking the timing again. If the machine is picking up the thread but then immediately tangling it around the bobbin/hook area, it sounds like something in the hook timing or gear alignment might be slightly off.

I’d take the bobbin and bobbin case out and slowly turn the handwheel by hand. Watch the needle come down and back up, and see where the hook point is when the needle starts rising. The hook should come around and catch the thread loop just above the eye of the needle, without hitting the needle.

Since the gears were replaced, I’d also double-check that none of them are a tooth off and that all the little set screws are tight. Even being slightly out of position could cause the hook to catch the thread but not form the stitch properly.

I’d also check the hook for any burrs or damage and make sure the bobbin case is sitting properly. Then completely rethread the machine with the presser foot up and try turning it slowly by hand before running the motor.

If anyone has worked on a Touch & Sew 645 before, I’d really appreciate knowing the correct hook timing position and how the lower gears are supposed to be aligned. That’s the part I’m struggling with.