Terry wrote:

How about some diamond coated (or similar) sand paper mounted to the
back of one of my turning tools. The magnet is only 2mm thick.

Not sure what grit would be best though. Maybe a 220 or 400? Then I
could flood that with water, and change it frequently. Just a thought.

Ed: What radius insert would you recommend for turning a ceramic
magnet that is 2mm thick. I am going from 12.5mm dia. down to 10mm
dia.

In spite of the fact that I don't know what I'm talking about, the
phrase "tool post grinder" keeps bubbling up to the top of my head --
the sandpaper will just make a set of grooves unless it's moving.

McMaster has diamond-tipped lathe bits, page 2370.

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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com