Hole centering adapter for hand grinder bit

thingiverse

I needed to drill pocket for flat screw head with my Proxxon hand drill. I had drill bit that could do the job and drill stand, but no means to center it properly on each hole. And it was number of holes I had to do. So 12 minutes later, including printing, and I got exact tool for centering. Centering adapter is matching bit diameter of 8 mm. How to use: Turn off grinder. Slide centering adapter onto machine. Turn it by hand to check if it is centered on bit. If it is centered peak of the adapter will stay in one place while turning. Place hole in working piece below bit, lower bit down so centering adapter gets into hole, and push it down gently until it positions in the center of hole (by touching hole edge). Fix working piece, raise bit, remove centering adapter, turn on grinder and drill. UPDATE: I had to enlarge inner diameter and change hole depth a bit for easier use. Model is updated. Corrected ID is 8.16mm.