I have an old Singer Graduate 6705 sewing machine. It has 4 screws on the bottom that once had rubber feet--all but one of those is long gone, and the one that remains is chewed into a nubbin.

So I designed and printed some new ones. I used Solutech flexible filament, which is pretty rubbery. I'm not sure how well these would work in PLA--I'd think they'd be too brittle to assemble and too hard to be useful.

To get them on the old screws, I just put the screw head down on the smaller end of the foot and gave it a firm tap with a hammer--the ring is flexible enough to fit around it and snap into place (though I couldn't get them in by hand).

That said, I'm including the scad file, so you can futz with the sizes on your own if you need to!