Well, I did it this time. The pivot was broken so I drilled out the arbor end .031 thousandths for a new pivot but on the LAST pass the bit broke off inside the new hole!!!. I've tried extracting the tip of the bit with a magnet, tweezers, etc but no cigar. This pinion is solid (machined) and very close to the end of the arbor. I may not have the tools at this point to remove the wheel and make a new arbor/ pinion, though this may be my only option now. If there is a way to recover at this stage, I'd like to try. Otherwise, I may need to outsource this one. Any suggestions?