I saw one of these in use, drilling holes in steel beams.
Just the thing for drilling holes in steel when you can't put the work
in a drill press. There's a large electromagnet that clamps the drill
on to the work. Terribly expensive, but I guess I could make or buy a
cheaper version using screw clamps

http://i7.tinypic.com/6763lew.jpg

Apparently it's a bit dangerous if the power fails while it's
drilling, because the magnet unclamps while the drill is still turning.

Matty F wrote:

Apparently it's a bit dangerous if the power fails while it's
drilling, because the magnet unclamps while the drill is still turning.

Since these tend to be used where reasonable sized holes are needed, the
rotation speed is unlikely to be that high...

I would expect there is more danger from the thing falling off and
landing on you without worrying about the spinning bits!

--
Cheers,

John.

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On Jun 27, 3:23 pm, John Rumm wrote:
Matty F wrote:
Apparently it's a bit dangerous if the power fails while it's
drilling, because the magnet unclamps while the drill is still turning.

Since these tend to be used where reasonable sized holes are needed, the
rotation speed is unlikely to be that high...

I would expect there is more danger from the thing falling off and
landing on you without worrying about the spinning bits!

I've always thought that those horrible small drill presses were
totally useless. But lately I've had to drill holes or drill out
rivets in pieces of machinery that are too large to put in a big drill
press.
Perhaps a small drill press could be clamped to the piece being
drilled.
It would be more accurate than a hand-held drill, and more force could
be applied using the geared arms.

"Matty F" wrote in message
ups.com...
I saw one of these in use, drilling holes in steel beams.
Just the thing for drilling holes in steel when you can't put the
work
in a drill press. There's a large electromagnet that clamps the
drill
on to the work. Terribly expensive, but I guess I could make or buy
a
cheaper version using screw clamps

http://i7.tinypic.com/6763lew.jpg

Apparently it's a bit dangerous if the power fails while it's
drilling, because the magnet unclamps while the drill is still
turning.


Extremely useful, and one of those tools I don't use very often, but
when I do practically nothing else fits the bill. Mine has interlocks
between the magnet and drill, so no drilling without the magnet being
on. Also you need to fit a safely chain when drilling upside down. As
others have said, the drill speed is slow, and they are intended for
the Rotabroach style of 'core drills' that remove a slug of metal
rather than everything coming out as swarf. Mine has a 2 morse taper
spindle so will also take normal taper shank drills, and plain drill
adaptor chucks as well as the 19mm Rotabroach adaptor.

AWEM.

"Matty F" wrote in message
ups.com...
I saw one of these in use, drilling holes in steel beams.
Just the thing for drilling holes in steel when you can't put the work
in a drill press. There's a large electromagnet that clamps the drill
on to the work. Terribly expensive, but I guess I could make or buy a
cheaper version using screw clamps

http://i7.tinypic.com/6763lew.jpg

Apparently it's a bit dangerous if the power fails while it's
drilling, because the magnet unclamps while the drill is still turning.


That is poor design..
it is quite possible to use permanent magnets to hold on and electricity (or
mechanics) to release.

On 27 Jun, 08:15, "dennis@home" wrote:

That is poor design..
it is quite possible to use permanent magnets to hold on and electricity (or
mechanics) to release.

Ah yes, Mr Genius strikes again, despite having never used either a
magnetically clamped drill, nor a magnetic chuck (with either sort of
magnet).

Have you felt the weight of permanent magnet chucks?

Have you used one of these drills at height, where they're often
needed to be used?

Have you seen the price of permanent magnet chucks, compared to
electromagnets?

Have you seen the complexity of making a permanent magnet chuck that
has a high force through a narrow pole piece and a large gap to the
workpiece? OK, so this is much easier with high-flux rare-earth
magnets than it used to be with with Alnico, but it's still hard. You
can make a higher flux with an electromagnet (and easily), so QE-
fecking-D.

The one thing we know about these drills is that they're going to need
a power supply to them. Power supplies are generally reliable, and
there are safety chains for those rare occasions when they're not.

Matty F wrote:

I saw one of these in use, drilling holes in steel beams.
Just the thing for drilling holes in steel when you can't put the work
in a drill press. There's a large electromagnet that clamps the drill
on to the work. Terribly expensive, but I guess I could make or buy a
cheaper version using screw clamps

http://i7.tinypic.com/6763lew.jpg

Apparently it's a bit dangerous if the power fails while it's
drilling, because the magnet unclamps while the drill is still turning.

Get yourself a cheap drill stand and glue some rare earth magnets to the
underside of the base. There is room under mine, the base seems to be
aluminium so the glue is advised.

Peter
--
Add my middle initial to email me. It has become attached to a country
www.the-brights.net

"Andy Dingley" wrote in message
ups.com...
On 27 Jun, 08:15, "dennis@home" wrote:

That is poor design..
it is quite possible to use permanent magnets to hold on and electricity
(or
mechanics) to release.

Ah yes, Mr Genius strikes again, despite having never used either a
magnetically clamped drill, nor a magnetic chuck (with either sort of
magnet).

Have you felt the weight of permanent magnet chucks?

Have you used one of these drills at height, where they're often
needed to be used?

Have you seen the price of permanent magnet chucks, compared to
electromagnets?

Have you seen the complexity of making a permanent magnet chuck that
has a high force through a narrow pole piece and a large gap to the
workpiece? OK, so this is much easier with high-flux rare-earth
magnets than it used to be with with Alnico, but it's still hard. You
can make a higher flux with an electromagnet (and easily), so QE-
fecking-D.

Who is talking about chucks?
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.


The one thing we know about these drills is that they're going to need
a power supply to them. Power supplies are generally reliable, and
there are safety chains for those rare occasions when they're not.

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

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?

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.

"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.

On Jun 28, 1:07 am, (Peter Ashby) wrote:
Matty F wrote:

Get yourself a cheap drill stand and glue some rare earth magnets to the
underside of the base. There is room under mine, the base seems to be
aluminium so the glue is advised.

I may end up making the whole drill stand. Sometimes there is not much
room for anything very high. Every job is different. In one job I'll
have to drill sideways into steel inside a small hole cut in concrete,
and the nearest power supply is hundreds of metres away so I may use a
generator. Or a long cable across a road! I am thinking about using a
number of welding magnets to stop the drill moving around, plus some G
clamps as well so I can apply force to the drill bit. It doesn't
matter how long the drilling takes. But a hand held drill would be
hopeless.