Tuning Machine HolesDrilling the holes is no big deal. I just mark them out and drill with a 3/8" brad-point bit. However, the tuning machine casting is metric and tapered, meaning that it doesn't really fit in a 3/8" hole.
I enlarge the hole with a #7 taper-pin reamer. Available from metalwork suppliers, they work sooo much better than the reamers sold by luthier suppliers. The slightly twisted one is spiral-fluted and the really twisted one is helical-fluted. I run them in the drill press at its lowest speed.