So on almost every Slant-o-matic I've had here, I've had this problem at some point. This week, it's on a Singer 431G (basically the lock stitch and chain stitch capable, open arm, German cousin of the 401A)
Test sewing on a "regular" quilting cotton or similar thickness (or lighter) other cotton, or cotton poly, 2 layers, no batting.
- The straight stitch is beautiful and no problems whatsoever. Tension well balanced right out of the gate.
- The zig zag stitch, or other decorative stitches will skip the occasional stitch, always on the same side.
- If I go to a thicker fabric, or fold the cotton so I have 4 layers, I have absolutely no problems.
- This occurs with or without upper tension adjustments when changing fabrics.
What I've done so far:
- All tests are done using a Gutermann Sew-All thread top and bottom, with a new Universal 90/14 Schmetz needle. (I may have also tried an 80/12 quilting needle, but it's a little dim, because it was a few days ago)
- I'm reasonably sure that the tension is right or at least equally balanced. i.e. they both could be a smidgen too tight or both a smidgen too loose.
- The machine has been fully serviced and oiled, both tensioners disassembled and cleaned and set back to the recommended setting per the Singer Adjuster's manual
- timing has been checked again and again. It's right as best I can tell ( the hook point is never -exactly- behind the needle at the mark on the needleshaft, it's usually a smidgen advanced, but no matter how I mesh the gears, I can't get it bang on. Also, all 5 of the Slants I have here have exactly the same timing, and I've only timed two of them - one that I changed the hook on (which sews beautifully now), and one that I should change the hook on, but filed the "curled burr from a needle strike" off the tip of the hook instead, because the hook that machine uses is rarer than gold plated diamond encrusted hen's teeth. )
I have never truly learned the presser foot tension rule, I generally just "futz" til it works, so my poor little brain feels like there's something there that's missing.
I can't help but think it's more sewing theory I'm missing, than something "wrong" with the machine.
Of course, I really want to hear other things I can try