there are other companies that will come out and calibrate you surface plate
and refinish if needed, our company uses Rockford Calibration, Rockford, IL
They use a tool that looks like a long block of steel with an indicator
mounted to one end, the indicator rides on some kind of shoe that reads in
the millionths I believe. He has a plate that he uses diamond dust on to
resurface the plates and they can fill in big gunges with some kind of body
filler.
we had them in for the last few years to do our plates, when they were in
the last time they found 4 of the small plates out of tolerance and it was
cheaper to by new ones than redo them, were talking about roughly 2' X 3'
plates. Ours are calibrated to .0005 and one of them has a hole thats .0045
in the middle from not being cleaned enough. We have the Starret Altissimo
height stands that we use along with the Brown and Sharpe stands. The
problem is that all shop grit lands on your plate and whatever you push
around on the plate pushes the grit into the voids on the plate. We've had
the plates for 10 years and we usually run 24/7 so they get plenty of use by
the operators.
If you had a good straight edge you could probably measure the gap under the
edge to find out how bad it is.

"Too_Many_Tools" wrote in message
oups.com...
A used surface plate just showed up on my doorstep...amazing what
follows me home sometimes. :)

This surface plate is a Rahn 34" x 36" black granite with two ledges.

So, how does one decide if a surface plate is "good"?

If it is "bad", how do you decide whether or not it is worth
refurbishing? How much does it cost to refurbish a surface plate and
how do they do it?

And if it is not worth refurbishing, what have you used an old surface
plate for? I've already got a gravestone. ;)

Thanks for any suggestions, comments or wisecracks.

TMT