The edge finder will run concentric when touching the work piece but you then need to advance until the edge finder kicks off. That is then the edge of the edge finder.

You then need to advance the axis a further 1/2 diameter of the edge finder to set on edge of work piece

Edit for smelling

Edited By ASF on 09/07/2017 18:18:02

As you say you have a DRO therefore when the finder kicks set the axis to + or – half the dia of the edge finder depending what side of the work you are touching off of. Saves having to zero twice.

Sometimes I put some bearing blue on the edge finder. You can see when it has a full contact just before it kicks off. My new one has a 10mm ceramic disc instead of the 6mm steel. The steel one is from like 1990 or so. Still works fine. I like the ceramic as it is anti magnetic. I found that if the part is slightly magnetic, or if the disc has got magnetised over the years, it reads incorrectly. So I run them over a demagnetiser periodically.

Neil