Members ThomasA Posted February 23 Members Report Posted February 23 @aslfkjaslfkjasflkj, just out of curiosity, did you ever solve this issue? I just had the exact same problem with uneven bobbin tension after adding an anti-backlash spring. It turns out that I have three models of bobbins. One, the old original, didn't spin at all. Three black was smooth as butter. 20 shiny ones from China jerked terribly. The original bobbin was too thick for the spring, but it worked fine without it. The spring is 0.5 mm. The other bobbins clear the spring OK, so that's not the problem. But it turns out, the 20 stainless ones is 0.15 mm larger in diameter and the center hole is 0.08 mm larger than the black ones and the original. It's enough for the bobbin to start rubbing and semi-bind to the bobbin case wall. The bobbin MUST only ride on the center post in the bobbin case. I reduced the diameter of a bobbin to verify my finding and yes, that was the problem. Quote
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