Tbh all its just to fix a small c@ck up on my shower mixer. I made the top and bottom holes too small to screw the chrome bits on. The spindles are 9mm so I was going to use them, bored out to centre the hole saw and make the hole in the panel bigger:
Blunt the sides of the pilot drill and put a couple of turns of greaseproof paper around it. It'll still make pilot holes and won't score up your bore. As soon as you have the tank cutter started remove the pilot to continue.
OR
Put the tank cutter through a piece of thin MDF and then tape the MDF over the place you want the hole. Use that to guide the tank cutter to start it off without a pilot.
Cheers all. Tbh I put the arbor in a vice and on the bench drill drilled a bit deeper with the Starrett HsCo pilot drill. Then went up in 0.5mm increments with ordinary, decent HSS. Used plenty of cutting compound.