Hey RonL,

What Footy says, but I do the X again after I've done the Y. That way
I'm more certain that I'm "seeing" the same kick of the finder. If
you're slightly off the quadrant line at the first X test, you will
note that the edge finder will be approaching form the opposite
"angle" on each side along any but the chord line through the centre.

And on my wobbly old mill, I figure that "dynamic" with the edge
finder is better than the "static" of a DTI. Works for me.

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXXXXXXXXX
On Fri, 14 Jan 2005 16:41:29 -0800, "Footy" wrote:

How about doing this?

Start with the edge finder approximately in the center of the hole. It
doesn't have to be exact. Move in one direction along the X axis until you
find the edge. Zero your DRO. Move in the opposite direction until you
find the edge. Note the reading. Move half way back to zero. Zero the
DRO. That is your zero for the X axis.

Then do the same thing in the Y axis.

The reason this works is that regardless of where you are in relation to the
actual center of the circle, you are traversing a chord of that circle. If
you bisect the chord and draw a line perpendicular to it at that point, the
line will go through the center.

This should get you accuracy as good as what you are doing and take a lot
less time. Just how accurate do you need to be?

And of course, all this assumes that the hole is actually round.