Re: [CAD_CAM_EDM_DRO] Magnets.....OT?

First off, I wouldn't use a car battery, I'd use a doorbell transformer (or
something about 12V at a couple of amps) and a 4-diode full wave bridge.
The pulsating DC will give you better magnetizing that straight DC. Number
of turns? As many as possible, depends on what wire size you use. You'll
have to size the wire to carry the current you can generate. We used to use
about 500 circular mils of wire size per amp of current. That's just a
starting point. Also, your chuck is made from interleaved north & south
poles (at least mine is). You'd make a U-shaped pole that would just span
one north-south pitch, magnetize there, then rotate just one pole to the
other side, magnetize there, and sort-of 'walk' the electromagnet down the
chuck, pausing at each step to do the magnetize thing (I dunno if you have
to leave the chuck handle engaged, or not). This will keep the proper N-S
orientation. Catch me off-list when you have more info, and I'll help if I
can.

RayHex

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> From: James Owens <wotisname@...>
>
> Hi,
>
> I hope the list Mom will forgive my OT but it is going on a CNC grinder.
>
> I have a magnetic table, for surface grinding, and the magnets have

become

> very weak. I have been told it is possible to re-magnetize them by using

a

> car battery and a coil. Can anyone tell me how? ie. How many turns and
> thickness of wire?