Grinding a magnetic chuck?

I have finally rebuilt my ancient Robot surface grinder, and would like to look at truing the magnetic chuck. I remember reading somewhere
that someone stated that the chuck must be in the "on" or "hold" position during the regrinding. I would have thought this might have caused problems in that the metal grinds would be held onto the chuck surface rather than being able to be blown free.
Can anyone give any advice?
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snipped-for-privacy@gmail.com wrote:

That would certainly be true if the chuck were of the electromagnetic variety, where it warms up due to the current running through it. If it's a manual chuck, I don't see why.
What I remember about grinding in a chuck from when I did my KO Lee was you use about a 46 grit wheel, dressed open, and flood coolant. Clamp the chuck upside down and take a cleanup cut all across the bottom, then mount the chuck (making sure you dial it in so the fence is dead parallel) and tighten it down, and grind the top until it comes clean. It may help to stone the corners of the wheel a little, to get a decent finish. My grinder isn't equipped with coolant, so I rigged up a suds pump using a bucket & pond pump & some tubing and fittings from the hardware store. Came out pretty flat, not perfect, but I can hold about .0002" over 12" which is OK for home stuff.
GWE
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That's pretty tight. I'd say there are very few applications where .0002" over 12" would be unacceptable - especially given the reality that blocks move with load, temp, time, etc.
Regards,
Robin
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