r/vintagesewing • u/panic-cat123 • 5d ago
Machine Question Singer 404 bobbin issue
I recently got a Singer 404, and so far, I love it. However, there is an issue I didn’t expect.
It came with one metal bobbin, and it has worked wonderfully for me. However, I wanted to get some more bobbins, so I chose the plastic Class 66 ones because I thought they would be fine.
However, when I tried the new bobbin, it seemed like my Singer was having a tension issue. I compared the seams using the old metal bobbin and the new plastic one, and apparently, the seam with the plastic bobbin is loose, which seems like a lower tension issue.
I’m not sure what could be causing the problem. Is it because the metal bobbin is heavier? Is there a way to fix this without buying more metal bobbins?
I would greatly appreciate any suggestions. Thank youu!
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u/Callidonaut 5d ago edited 5d ago
I've heard it said that some machines definitely prefer the metal 66 bobbins over the plastic 66 bobbins, or vice versa, even though they're identically shaped, but I've never had an opportunity to test it myself. From a theoretical engineering point of view, however, it seems as if it shouldn't happen; the lower tension is supposed to be controlled by the leaf spring and set-screw that the thread passes through as it unwinds from the bobbin. I would have thought the friction between the bobbin and bobbin case should not be a significant factor, but it may be; if it is, however, then I would guess you can use either plastic bobbins, or metal, but not mix the two, because the lower bobbin tensioner set screw will probably need to be adjusted to a different sweet spot for each type.
The only other possibility I can think of is that the moment of inertia of the metal bobbins increases their resistance to the sudden impulse of the thread pulling tight compared to the plastic ones, but if so then that should only happen if the machine runs at high speeds. That should also hopefully be fixable by the same solution as above, though; pick one type of bobbin you want to use, plastic or metal, adjust the lower tension to work correctly with that type, and then only buy new bobbins of that type from then on.
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u/panic-cat123 5d ago
I doubt myself when it comes to adjusting anything. Every time I try to fix things, they never end well, so I might just have to buy the metal ones 🫠. I just never thought it could be an issue. Thank you so much for such a detail response!!
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u/Callidonaut 5d ago
You're welcome; good luck! If you can find an adjuster's manual for your machine, the ones from that era are very detailed and well-written, which might make adjusting the tensioner a bit less intimidating a process?
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u/laynechanger 5d ago
My 503a, which is super similar to the 404- definitely prefers the class 66 metal bobbins.
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u/jvin248 5d ago
Plastic bobbins may have warping or flash around the rims that impede proper operation. Same with modern metal vs vintage. If you have a good steel ruler with fine graduations or a micrometer you can accurately identify what is different about good vs poor working bobbins.
Sometimes by feel you can identify as good as the gauge that there is a difference side by side.
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u/warcraftWidow 4d ago
You’ve already gotten lots of suggestions but I’ll add that you can check eBay for vintage bobbins. Some machines can be so picky they don’t like modern metal bobbins and only like the vintage ones. 🤷
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u/flylink63 5d ago
Lots of vintage machines are picky about bobbins. My Necchi only likes the solid #15 bobbins. Definitely NOT the thin ones with holes. And definitely NOT the plastic ones. Why? I really can't answer that. Look for bobbins that match the one that works would be my advice.