Cutting AlNiCo

[cryptozoo]

Has anyone here had any success cutting AlNiCo magnets into specific shapes and sizes?

[Peter Naglitsch]

Done it, yes. With success, no. I have tried cutting Alnico bars into half with a diamond cutting wheel on the dremel, constantly cooling it with a damp rag so to not get it too hot, thus messing with the material. It was no success. They still got too hot and the magnetic strength is only about 1/10 of that of the original sized bar

[Possum]

....

You can cut alnico with a tile cutting saw, its slow going but you can get one for $50, you need to cut them wet...

[EFK]

I cut an alnico 4 bar mag from 2.5" down to 2 1/4" by using a dremel cutoff wheel to score both sides fairly well, clamping it in a vice (with only the 1/4" to be removed protruding) then whacking it with a ballpein to snap it off. Somewhat similar to cutting glass. It broke very cleanly along the score lines and then I just used a big grinding wheel to very carefully smooth the break- kept dipping it in water to keep it from heating. No effect on the charging. Dust leaves a really bad taste in your mouth - I'd bet you should not be breathing that dust.

[cryptozoo]

Interesting, thanks for the comments. I'll give the tile cutter a try, I think I've got one somewhere from an old bathroom redo. Def wouldn't think the dust would be good to inhale (especially if it's already magnetized -- yikes!)

[peskywinnets]

I recently tried cutting some 5mm alnico magnets...man what a job it was too.

Don't laugh, but my approach was to mount a dremel in my CNC (vertically), then insert the alnico rods into some predrilled holes so they stood vertically below the (vertical) Dremel), I then moved my dremel sideways 'into' the rod using the CNC machine controls (the dremel had those diamond cutting disks in it's collet holder). It worked, but you're looking at about 15 minutes per cut!

The problem with the above method is the 'drag' on the cutting wheel as it progresses through the rod. A far better way (& will be my next approach), would be to find a way of mounting the dremel horizontally on a lathe (ie on the tooplpost) & inserting the Alnico magnets into the lathe's chuck - at least this method, the alnico turns in the chuck so the Dremel cutting wheel won't get bogged down with 'drag' so much (as it'll always be cutting the outside ege). It'll still be awkward as hell...but it's the only way I can get Alnico in the size I need (6mm diameter x 6mm long)

[Peter Naglitsch]

If you need a bit more that only a few of those 6mm long 6mm rods, you might consider Sensmags. I have an order on the way from them and they seams to be nice quality (electricdave was very generous and sent me a few from his batch to try our) with decent prices and they can do ANYTHING in custom sizes, not only what they have in the catalog or on line. I included some custom magnets in my order and I think the prices were excellent for custom items.

[Joe Gwinn]

Done it, yes. With success, no. I have tried cutting Alnico bars into half with a diamond cutting wheel on the dremel, constantly cooling it with a damp rag so to not get it too hot, thus messing with the material. It was no success. They still got too hot and the magnetic strength is only about 1/10 of that of the original sized bar

Use an aluminum oxide cutoff wheel. If you try to cut ferrous alloys with diamond, unless the tool is turning very slowly, the diamond tool will be ruined. The problem is that diamond (a form of carbon) dissolves in hot iron.

Also, flood the alnico bar with water while cutting, so it doesn't overheat.

[Peter Naglitsch]

You are right Joe. I actually didn't use a diamond wheel. I remember now. I used one (several) of their standard abrassive cut-off wheels. And cooled the alnico with water every fifth second or something like that. It still lost most of its magnetic "capasity"

[Joe Gwinn]

You are right Joe. I actually didn't use a diamond wheel. I remember now. I used one (several) of their standard abrasive cut-off wheels. And cooled the alnico with water every fifth second or something like that. It still lost most of its magnetic "capacity"

It takes more than a red heat to demagnetize alnico, so overheating is not likely to be the problem. Wiki on Alnico

If an alnico magnet is too small compared to the air gap it must drive field through, it will lose its magnetic charge. Rare earth magnets can be far smaller for a given field in the air.

[belwar]

I had read somewhere that you can cut alnico with Carbide Tools.

If someone wants to post the comparative hardness (in comparison to 1018 steel) i'll try cutting some on the CNC today. I've got several different grades of carbide tools and a vise mounted in the machine right now.

b.

[Peter Naglitsch]

It takes more than a red heat to demagnetize alnico, so overheating is not likely to be the problem.

Hmmm. You live and you learn. Anyhow its not possible to charge them higher than aprox 300 Gauss using some supersized Noe magns. I must try to zap those halves once I got my magnetizer together (having a few critical parts made by a friend right now) and se what happens.

[jonson]

This question has come up quite a few times now including bits by myself and as it is something I do need to do then I have spent a long time pratting about with it. Forget the Dremel it's not the tool for the job. It has it's uses but needs to be filed with a lot of other stuff as hobby fodder. Joe hits the nail on the head with ali,oxide blades for Alnico but go for the hard Inox stainless ones at a min 4.1/2 in diameter. It's a fairly simple and quick job to split a bucker mag if you do it the right way. I avoid water and use steel plates and clamps as heatsinks and the magnets are handleable immediately with no discolouration and very little loss of power. Belwar you are correct that alnico will cut with carbide but it needs to be the right grade and forget the cnc unless yours has built in feeling, cus thats what you need. You have to feel your way into the cutting not let a machine just run as it's programmed to do. Unless your machine runs on A.I.
Diamond is ok for ceramic but these home tile jobbies leave a lot to be desired. Too much wobble and not enough speed. Dicing saws and blades run a far higher speed and the blades are thinner but run at $6000 upwards and you need a lot of work to justify that, but blades are sold seperately and you could make your own homebrew cutter and use cutting fluid not water. The other thing that crops up is cleaning the particals off the mag afterwards and the airborne dust. Wear a mask but even though I do I still do not worry too much about magnet dust. Iv'e spent hours on the grinder and then placed my still white mask under a microscope and found nothing, as nearly 99% of that dust is stuck to the inside of the shielding round my bench grinder wheel. The one that concerns me more is the big pile of stone dust on the bench under the wheel and that stuff does get airborn, so hence my reason for wearing a mask. You do all that then someone suggested blowing the dust off with an airline... Now it is airborn.... and gonna stick to anything metal there is laying around or your clothes or skin so go the easy route. Running water which needs not be very fast, a common or garden fingernail brush and a bucket under the tap.(fawcet) I think stateside. Just brush the dust away from you into the bucket (plastic) under the running water and also place a steel plate or block in the bucket to collect all the dust. Builds up a good pile after a few years for you to think of things to do with. Water goes on the garden or house plants not in your coffee.
There you go Iv'e ranted on again, but as long as it helps a bit then good enough.

[David King]

Aspect ratio for alnico to hold a charge

Alnicos have a hard time holding a charge if they are cut too short. I think the length needs to be at least 2:1 of the dia or width. 5:1 and longer is best.

[Amplexus]

alnico can be ground with id/od and surface grinders, run plenty of coolant and slow feeds and preferably grind before charging.
Amplexus