This is a nut that I can hand tighten to hold my Dremel in a jig.

It's a 3/4" 12 tpi thread nut that will clamp the Dremel to a 2mm thick plate. The hole in the plate is 19mm.

If you use a thicker plate then you should drill the hole 25mm so that the larger shoulder seats on the surface. My plate is 3.7mm thick and the recess is 2mm.

On my printer I printed it scaled 101% in the radial directions to make the fit slightly looser but 100% threaded on fine

Lay it on its front face to print