Customizable Spanner, enhanced

The original required you to figure out the diameter to use to get a properly sized nut driver. This version does the calculation for you, you just tell it how big of a nut you want.

(math nerd stuff: nuts are measured flat to flat (circumscribed hexagon), but the OpenSCAD trick for making hexagons measures vertex to vertex (inscribed hexagon). This does the math so you don't have to. It also makes it easy to just pull the size to print on the face of the wrench.

I also added a user-defined clearance so you can tune it for your particular material, printer, and settings.