XO-1 spur-to-pinion adapter that includes the "Cush Drive"?

[Dr_T]

Finally tried preparing the Traxxas XO-1 cushdrive key for use as spur-to-pinion adapter, but wasn't very successful...

With a lot of effort I managed to drill a 2.5 mm hole in it (HSSE Cobalt drill), but then it cracked when I tried tapping the M3 thread (at about 1/3rd in). The material is extremely hard and it took very long to drill the hole, maybe because of that the hole needed to be a bit bigger diameter for the thread to be tapped?