Thanks for showing your method of slowing your 31-15 down. I like the looks of it, but I don’t have a lathe to make one.
The three ways that I have seen work to slow down a Singer 31-15 are:
Slow: On one of my 31-15s I put together a home-made speed reducer out of pulleys, bolt, and bracket. It made about a 4:2 ratio, which wasn’t quite slow enough. It reduced the speed by about half (1725RPM motor), but the machine was still fairly speedy.
Slower: I had another 31-15 that came to me with an Atlas Clutch on it that was an early style of clutch motor. The motor and clutch are two separate units. The clutch slippage can be tweaked to get a slower speed, and I’ve heard that operators even greased the cork clutch surface to increase slippage. Whoever had this one before me had tuned it very well, and I was surprised at the slow control that I could achieve.
Slowest: My go-to Singer 31-15 is in an industrial treadle. I have no problem sewing as slow as I want. I also have a 31-15 that I’m experimenting with a spinner steering wheel knob on it to use for hand operation. It should be slower than the treadle.
CD in Oklahoma