On Aug 15, 1:15*am, Don Foreman wrote:
On Thu, 14 Aug 2008 19:43:47 -0700 (PDT),
wrote:...
Here is a question: *Has somebody here actually TESTED an edgefinder
to determine accuracy and repeatability?
...
Wolfgang
...I trust my best edgefinder to half a thou, though I very rarely *need
that kind of accuracy. *

I checked how repeatable mine was the other day because of this
thread. It repeated to about half a thousandth turning at 600 RPM on a
filed surface and I could get it within a thousandth by feeling for a
step when it was stationary, which is how I use the center finder.
When I want accuracy I surface-grind the block before milling and
drilling. A surface-ground edge seems to behave differently with an
edge finder, maybe it's the friction or lack of it?

I haven't made anything recently that could be used to check the
accuracy of the edge finder. Maybe a carefully bored hole near an edge
would do.