"Andy Dingley" wrote in message
...
On Wed, 27 Jun 2007 20:22:58 +0100, "dennis@home"
wrote:

Who is talking about chucks?

They're a controllable magnetic clamping device using permanent magnets,
big enough to resist a significant force.

Thanks but I know what they are but as I said who was talking about magnetic
chucks?

You're talking about quite a
different device from the sort of magnetic base used under a DTI

DTI?
Am I talking about them?

Its a magnetic base and need not be heavy or complex.
You can buy a magnet with 250kg of load that only weighs about 100g.

So how do you remove it, if it's not switchable?

Its not difficult to switch them, all you need is some sliding iron bits.


Most importantly, a "magnet that holds 250kg" is talking about an ideal
situation against flat steel. That's not the working conditions a
magnetically clamped drill has to cope with.

You need a lot of coils or a lot of current to do better.