I’ve got an electric Singer 319W that I’ve never used, a treadle Singer 319W that I’ve used quite a bit and used today to mend denim jeans, a Singer 306W that I used quite a bit in the treadle until I got the 319W that replaced it, and a Singer 206K set-up for treadle that I’ve never used. I use only 206x13 needles in all of them because that’s what they call for. I use these machines for mending denim jeans with a multi-zigzag stitch and Coats Dual Duty+ poly-covered cotton thread. The size 12 needles that are readily available work just fine for what I do.
I switch to a different machine if I want to go to thread that requires a size 14, 16, 18, or larger needle, mainly because I have other machines and don’t want to mess with changing the tensions. I’m spoiled, I guess, but I don’t see pushing a machine to do something that it’s not designed to do.
CD in Oklahoma