I have a Sherline 5000 MANUAL mill, that I need to know how to find the center of an unbored pinion gear to bore a .198" hole. I thought you would find the edge first using an edge finder, but being that the pinion is round it would seem useless since after finding the edge I would still have to fiddle with the X and Y axis hand wheels to get the cutting bit to hit the exact center of the round pinion. So how do I go about doing this? I know the math way to find the center of circles obviously, but trying to adjust the dials on a mill in the real world is a whole different story.

One other question I have is how do I properly secure this so that it is perfectly level to insure a straight hole?