
[img]https://.backpages.carpokes.com/guestpics/dimpledie/rivet-style.jpg[/img]

You can print these in just about any filament -- PLA, ABS, PETG, etc. -- just crank up the infill to 75% or so. No support needed. They work over and over and have been tested on steel up to 18 gauge (22 gauge shown in pictures).
These are all set up for a 1 inch hole, but virtually all slicers will let you scale to whatever size you need. For example, if you need a 1.5 inch hole, just scale it to 150%. A 20mm hole would be 20/25.4 = ~79%, etc. Just be sure to use "uniform" scaling or otherwise make sure at least the x and y axes are scaled the same. (You can play with the z axis if you want to adjust the depth).
