F. George McDuffee wrote:

FWIW -- I have always had the spindle turning [c. 500 rpm] when
using the electronic edge finder. Also very careful sneaking up
to a contact. Light is not very bright though when it makes
contact.

Unka George:

If the electric edge finder is spinning, AND if it runs out a little,
it will probably light up when the high point contacts a conducting
surface. But you really won't know if that high point is .0001",
..001", or even .010" off center. That's why I would contact your part
with the edge finder stopped (then zero out your axis), back off your
part, turn the edge finder 180 degrees and contact your part again to
see if there is a difference in the two positions of the edge finder.
Half that distance difference should be your off-center runout


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BottleBob
http://home.earthlink.net/~bottlbob