Quote Originally Posted by mparker762 View Post
Wouldn't these stones chew up the machine shop's surfacing bits? They are very abrasive after all, and I suspect a carbide bit designed for steel won't take kindly to milling ceramic. For that matter, the barber hones might not take kindly to being milled that way either - many of these hones are very brittle and fragile and can't survive even a drop onto linoleum.
You would not mill one of these [hone]. You would grind it on a surface grinder using a diamond wheel (or maybe even less). I've never trued a hone but a shop I worked for did true granite check blocks in a similar fashion (these have to be incredibly precise as they are used to take measurements off. usually within .00005").
You would not hunk right into the stone (that would cause it to break/crack and could destroy the wheel. very expensive to replace $$$) with the grinder. You would take several light passes that each would take off less than a hair width. Most likely they would marker the top surface were you can see at which point the stone is level (I would), then do an a final pass for shits and grins. I used to do the same technique to level carbide stamp tools. Carbide is also very brittle.