According to Alan Rothenbush :

So I bought another mag chuck for my little Sanford Surface grinder.

[ ... ]

Needless to say, the grease inside it has gotten THICK and HARD and so
engaging the magnet is HARD WORK.

[ ... ]

It's basically five major pieces,

. a pair of end plates (angle brackets, really)
. the top
. the bottom ( a single piece of flat steel 4" x 8" x 3/4") and
. what I assume is a magnet, because it's what you rotate to "turn it on".

The "magnet" looks like nothing more than a 1.5" diameter round shaft covered
in old grease.

So, I can just dump the whole thing into a tank of solvent for a week, hope
the grease dissolves, hope I get all the solvent out and then hope I can get
fresh grease into all the places it needs to go.

Or I can remove four more allen screws, disassemble it completely and
clean it properly.

Here's the question. If I disassemble it completely, am I likely to
demagnetize something somehow ?

To disassemble it, you need some way of replacing the magnetic
circuit around the permanent magnet. And I don't know whether this is
really possible. Some PM chucks were polarized by an external magnetic
pulse applied through the pole pieces after assembly. Disassembling it
risks serious weakening of the field strength, leaving you with *two*
chucks which are too weak.

I would either try the solvent approach, or perhaps the heat
one, as long as you don't go too high in temperature, as that, too, can
degauss the permanent magnet.

Of course, if you had a service in town which could re-polarize
your chuck, disassembly would be the way to go.

Good Luck,
DoN.

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