On 2010-11-18, Wes wrote:
GeoLane at PTD dot NET GeoLane at PTD dot NET wrote:

On Sun, 14 Nov 2010 17:30:09 -0800, Gunner Asch
wrote:


This one runs ok, but is dirty and nasty. The 6x18 magnetic chuck needs
repair..a pin inside has come loose and it doesnt go fully into Engage
position. Not a big deal

I've got a fine pole magnetic chuck that doesn't work as well as I
suspect it should - there are strong areas and weak areas. I"ve read
various opinions on the web regarding whether it's safe to take them
apart versus those which say they'll lose their magnetism and be
ruined. How do you tell if the one you're working on will lose its
magnetism if you open it? The chuck in question is a Magnetool, from
Hazel Park, MI.



I think you have been told a wives tale.

Which type of wife -- old -- or young? :-)

Actually, it does depend on the type of permanent magnet. Older
magnetic materials will only retain a certain amount of magnetism if the
field strength falls below a certain level, and disassembling it opens
the magnetic circuit so you do lose the strength. It requires a special
fixture to re-magnetize to the original level.

However, modern rare-earth magnets seem to not have this problem
-- at last at the field strength levels involved in magnetic chucks.

So -- the older it is, the more likely that it will suffer from
being disassembled.

Now -- if the magnet and carrier remain in contact with the pole
pieces, you probably won't hurt anything. But if you separate them (a
major struggle with a good one), you will lose field strength -- unless
they have started making them with the rare earth magnets. (The same
applies to the dial indicator holders and to stepper motors too, FWIW. :-)

Good Luck,
DoN.

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