I'm locating the center of some holes .500" dia with a Starrett edge
finder.
The tip of the edge finder is .200. I'm just not sure if I'm doing it
the
BEST way.

Go to http://www.geocities.com/mklotz.geo/ and get osborne.zip and read
the .txt file. You have to accurately measure your hole diameter but
then this procedure will converge to the hole center in two or three
iterations with better accuracy than simply bisecting the x and y
chords.

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Regards,
Carl Ijames carl.ijames at verizon.net