CAUTIONARY NOTE

your printer needs to be very fine-tuned to make this part perfectly concentric.  If it is not perfectly concentric, your hexagons will be imperfect - when I attempted this, the hex ended up being ‘tilted’.  On a hex measuring 1.95mm flat-to-flat, it was tilted by 0.10mm.  The model itself is perfectly concentric/hexagonal.

Background

I needed to make some tiny hex keys for mouse wheel encoders that were non-standard sizes.  I had an R8 arbor for an ER16 collet set.  I did not have a hex block.  It turns out, there's no such thing as an R8 hex block because the R8 spec can't pass stock through - any hex blocks out there were DIY (or very very expensive compared to a 5C collet system).

Anyways, this works just fine aside from the printing tolerance note above.

Other materials

You will need a ~50mm bolt (M12x1.75 for mine) to secure the arbor.  I also left an extra 5-10mm in the bottom for ‘my arbor is too long’ problems.

I used a fine-tip sharpie to colour in the letters.

You will obviously need an R8 arbor of some flavour.  :)

Usage & functionality

The hex block was not the weak part of my milling setup.  Functionally it worked perfectly (aside from print tolerance thing noted above).  

Printing recommendations

• 40% infill, 4 perimeters, Prusaslicer 0.15mm STRUCTURAL preset, gyroid infill pattern.
• In one of the pictures you can see what happens when you use 0.20mm, 2perim, 0.20mm SPEED settings.  Both models were subjected to the same test - the vise easily crushed one, and I was afraid of breaking the vise on the other.  (PLA+)
• Print vertically, with the bolt hole on the print plate - no supports required.