Cutting Alnico Magnets?

[SlidePicker]

quartz crystals, their hardness rating is 8, I think alnico is around 12 or something...

That's on the Moh's hardness scale that goes to 10 (diamond.)

[pdf64]

Hi, I remembered this from Kinman.com

"42) Can I grind a magnet to reduce it's height?

Definitely not. Grinding or filing magnets will cause irreversable loss of magnetic properties. The magetic material (metal alloy) is carefully heat treated during manufacture to bring out the desired magnetic properties, excessive mechanical vibration and heat can alter or even destroy these properties."

I've never tried it but the above advice sounds worth considering.
Peter

[Spence]

Simply not true. Why not ask Mr. Kinman to prove what he says.

[ken]

Mr. Kinman is 'kinda sorta' right...

Grinding a magnet will make it hot in a hurry, and according to my reference books overheating Alnico will permanently demag it. So, I have to find a method
of cutting that will work. Joe Gwinn was right, there has to be a way to do it cost effectively, or buying precut magnets would not be cost effective.

Ken

[Spence]

I grind AlNiCo to length every day. If you get it cherry red you will lose some magnetism. It's easy to recharge it though with a pair of neo mags. I have also cut AlNiCo rods with a dremel. It takes time but it can be done and then you'll have to grind the surface then to get the exact length and a flat face. You can sand AlNiCo. Just try it. For instant bevelling there's nothing easier than mounting an AlNiCo slug in a drill and spinning it at an angle againt a sanding belt.

[Steve A.]

I grind AlNiCo to length every day. If you get it cherry red you will lose some magnetism. It's easy to recharge it though with a pair of neo mags. I have also cut AlNiCo rods with a dremel. It takes time but it can be done and then you'll have to grind the surface then to get the exact length and a flat face. You can sand AlNiCo. Just try it. For instant bevelling there's nothing easier than mounting an AlNiCo slug in a drill and spinning it at an angle againt a sanding belt.

Spence- I think that Chris Kinman was referring to a customer trying to grind down the slugs in an existing pickup. And I think that page goes back many years, long before the idea of charging slugs with neo magnets was presented here (I think we all pictured the old Fender factory with that huge machine used to charge the AlNiCo slugs... Or bringing our pickups down to a machine shop in the seedier part of town.)

Steve Ahola

P.S. I'm wondering about cutting AlNiCo bar magnets to use in a Firebird style mini-humbucker... any luck using a dremel for that?

[Spence]

Yup, no problemo. done that too. Just be patient, take your time and be prepares for lots of dust from the cutting discs. Oh, and you'll probably get through two or three of those in the process.

[ken]

I learned something else about Alnico... the cobalt in Alnico is toxic if it is absorbed into your body, so if you are cutting or sanding the stuff please wear a respirator!

Ken

[Joe Gwinn]

Diamond blades are not good for iron alloys

One thing strikes me. Diamond blades are not good for iron alloys, such as alnico, as diamond (a form of carbon) dissolves quite easily in iron. Use aluminium oxide instead.

[Possum]

cutting discs

in the lapidary industry, like in Brazil they don't use $100 diamond discs you buy for retail. they use industrial diamond dust slurry and metal blades, you can't buy diamond dust retail, at later stages they use carbide slurry, same method. I've cut bars with my diamond water cooled band saw but after about five cuts the blade is just about shot. For rods they are a quicker cut to do being smaller, the water cools and lubricates and washes away the dust. In the old days some guys cut rocks without water or coolant, you have to wear a good mask, some minerals do real bad things to you. I forgot what mohs alnico is but its real high. I looked at some tile saws today don't know what abrasive is in the blades, a larger blade is better, they had some there for about $50, cheap chinese stuff I guess....for cheap you could do what Spence does, score with a cut off disc and dremel break the score and grind and sand the ends.

[Spence]

You can cut right through the AlNiCo with a dremel cutting disc which is what I do rather than scoring them around the edge. I would be a little concerned about the alloy's brittleness to try scoring and snapping. In any case, Dremel cutting discs cost peanuts so it's less of an issue than anything with diamond dust/slurrey. The trick is to be patient because the Dremel discs can shatter very easily.

[Joe Gwinn]

in the lapidary industry, like in Brazil, they don't use $100 diamond discs you buy for retail. They use industrial diamond dust slurry and metal blades, you can't buy diamond dust retail, at later stages they use [silicon] carbide slurry, same method. I've cut bars with my diamond water cooled band saw but after about five cuts the blade is just about shot.

Right. You cannot use diamond to power-grind iron alloys, even with water cooling. What happens is that at the point of contact between abrasive particle and metal, the temperature is very high, and the diamond simply dissolves in the iron. This is well-known in the metalworking industry.

Diamond works OK for wet hand grinding steel, if one isn't too aggressive.

I forgot what mohs alnico is but its real high. I looked at some tile saws today don't know what abrasive is in the blades, a larger blade is better, they had some there for about $50, cheap chinese stuff I guess... .

Alnico is probably about 7 or perhaps 8; it cannot exceed diamond, which is 10. Pure cobalt is 5.5 Mohs. Alnico can be ground by aluminum oxide (9 mohs) and silicon carbide (9-10 mohs).

Anyway, a blade using aluminium oxide and/or silicon carbide, cooled with water or soluable oil, ought to work just fine. One can use a soft metal blade and an abrasive slurry in a bandsaw-like saw. A lapidary saw with an aluminium oxide blade ought to work.

[ken]

Thank you...

Until now I had no idea that diamond will actually dissolve in iron based metals. I looked it up in my chemistry and machining books, and you seem to be right. Diamond is a form of carbon, and iron type alloys (like Alnico) when heated absorb carbon readily. So now I'm looking for an aluminum oxide blade. I bought a diamond blade already, I'll use it to test a saw. Now I'm looking for an 'oil' type
coolant pump too...

Ken

[David Schwab]

I learned something else about Alnico... the cobalt in Alnico is toxic if it is absorbed into your body, so if you are cutting or sanding the stuff please wear a respirator!

Nickel is also toxic. And Aluminum deposits in the brain are thought to be one cause of Alzheimer's Disease.

Always wear a respirator anytime you make dust!

[Joe Gwinn]

Nickel is also toxic. And Aluminum deposits in the brain are thought to be one cause of Alzheimer's Disease.

Always wear a respirator anytime you make dust!

Life is easier if you always cut wet. The cutters work better too, as the fluid keeps the business end cool.