Depends on what the magnets made of. Some are the cheapy elastomer
strip kind. They'd be very easy to drill, cut and mutilate. Others,
like alnico, are metallic so I'd try a regular 'ol twist drill. Some
magnets are ceramic. Those are very hard, like glass. Maybe too hard
to drill. And still others are sintered, but they're also quite hard.
I've not seen them cut.
However, the machinist guys would know more.
In your application, I'd make a pocket to fit the magent in and then
use an adhesive like gorilla glue or epoxy to stick it in place.
That's certainly easier than trying to drill and screw it in place.
This has to be one of the most helpful newsgroups I've ever seen.
That Lee Valley place has a few solutions for what I'm doing, so it looks
like I won't have to drill after all.
If you TRUELY have to drill a hole, it's possible, but not fun at all in
either a AlNiCo or rare earth magnet...doable, but not fun.
The biggest problem you'll have is that most woodworking machines won't go
slow enough to do a good job, but this will still work...assuming that you
have a drill press...
Get a piece of copper tubing that is the diamter of the hole you want and
some diamond powder or paste...if you get the powder, you'll also need some
olive oil. You'll also want some vaseline or other petrolium jelly.
Using a vise that will hold the magnet well and solid, center the drill
chuck over exactly where you want the hole in the magnet and build a damn
around the magnet with the jelly.
Mix a teaspoon or so of the diamond paste with some olive oil...needs to be
pretty think and stiff, about the consistancy of grease or maybe a little
softer...put about 1/3 to 1/2 of this mix on the top of the magnet.
Chuck up the copper tubing in the DP and set it at the lowest speed you
have. Turn on the spindle and SLOWLY and GENTLY pull the tubing into contact
with the magnet and pull for a moment...call it 2 seconds... and release.
Raise the tube and rearrange the paste to fully cover the magnet again. Do
this a couple of times...what you are doing is calling "charging"...basicly,
embedding the diamond grit into the copper and then the copper becomes your
Pull the tube into the magnet and it should start to cut a ring the size of
the tube...keep the area filled with the oil and occasionaly fill the groove
with more of the paste.
WARNING!!! This can be a messy operation!!!
It is sorta possible to drill an AlNiCo magent with a carbide drill, but it
will often fracture the magent and when it doesn't fracture, it can still
lose a lot of power due to the heat generated. Using the tubing method, the
heat is kept to a minimum. Sorry that I can't tell you how hard to pull or
anything like that...it's one of those things that I know what I know and
how to do it, but I can't describe it without showing it.
Any other questions, feel free to ask.
I agree with the posters who say to try glue,
but if you must drill it . . .
If the magnet is metal try a cobalt drill bit. Most good
hardware stores carry them. My local Ace does.
If the magnet is ceramic go to http://www.baddogtools.com /
and click on Drill Bits. I've seen these demonstrated and they
will go thru extremely hard metal files, ceramic, glass, rock,
and cement. I've never tried them personally but think they
should work for you.
Be aware that you will weaken any magnet by removing
material from it. You can also weaken a magnet by heating
it, so when drilling be sure you keep it cool by flooding it
with water or other coolant.
You are in for a rough time, instead of drilling get a magnet with the hole
already in it. You can buy these at most hobby type stores or order from a
company such as Lee Valley or Highland hardware. Cost will be less then
special bits and it will not lose power. Since you are embedding it in a
door what I would do is drill my hole in the door to the proper size and use
epoxy (5 min works ok for wood or metal slower epoxy works a little better)
to hold it in place. I attach magnets to the surface of wood quite often
this way and have no problems, in a hole it would work even better. Mix the
epoxy on paper and rub the magnet in it, then place in door, clean up waste
epoxy before it fully hardens. Should be good for a few years.
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