1. Measure grub screw or tiny allen bolt.
2. Get the right drill bit and tap. (How to work that out
3a. Now drill a pilot hole in the middle of the beveled out bit. do this by measuring from the edge you beveling in half the amount you beveled in. (I measured 4mm as I beveled 8mm)
3. Use the larger drill bit and drill threw the pilot hole of the bar end.
4. Use the tap remembering 1/2 turn 1/3 back or whatever you want.
5. Check the grub screw fits.