Screw holes

How big need holes to be in your material so a self-cutting screw is just comfortable?

I didn't know either, so I made this thing to try it out.

The holes go from M2 (d=2mm) to (almost) M8 (d=8mm) in increments of d=0.2mm.

It was made in OpenSCAD, source is here: https://github.com/jernst/openscad/blob/master/calibration/screwholes.scad