Turning Ceramic Material on a Lathe

You probably answered your own question. Unless you have a "machinable" ceramic like Macor or lava you'll need diamond tooling. I believe diamond tipped inserts are available. Randy

The company we purchase them from can machine them, but the lead times are very long and we just can't wait. They did say we should use diamond tooling, but I have not seen any diamond coated turning inserts. I will have to look a bit more.

Thanks

Look them up on Google. They've been around for some years now. I was writing articles about them back in the '90s.

-- Ed Huntress

How about some diamond coated (or similar) sand paper mounted to the back of one of my turning tools. The magnet is only 2mm thick.

Not sure what grit would be best though. Maybe a 220 or 400? Then I could flood that with water, and change it frequently. Just a thought.

Ed: What radius insert would you recommend for turning a ceramic magnet that is 2mm thick. I am going from 12.5mm dia. down to 10mm dia.

Thanks

Got a toolpost grinder? Carbide or diamond grit burr/stone?

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

Search term "PCD Inserts"

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

In spite of the fact that I don't know what I'm talking about, the phrase "tool post grinder" keeps bubbling up to the top of my head -- the sandpaper will just make a set of grooves unless it's moving.

McMaster has diamond-tipped lathe bits, page 2370.

I don't know of any such sandpaper (it may be around, I've just not heard of it), but how much material do you have to remove?

First, that kind of unusual-but-practical information is not something I would know from experience. My way of finding out such things is to look it up or to go directly to the experts and ask them. This is 'way outside of my knowledge.

Second, if you have to remove 2.5 mm of hard material, I think the sandpaper idea will become a career , but you'd better get some other opinions.

Third, although I have no specific info, here are a couple of general ideas. Sintered ceramics usually are ground, not single-point turned. When they machine engineering ceramics in production it's usually done with green (unsintered) ceramics, or with glassy ceramics that are made to be machined (Macor, for example).

I don't know anything about the machining properties of magnet ceramics. In general, again, you turn or mill friable materials with the smallest cutting edge and the slightest feedrate you can -- a sharp tool, in other words.

But ceramics vary widely in their properties, and this is one you could only learn from experience, unless you trip across someone else's account of how it's done -- from experience.

Good luck. Probably it's doable, somehow. I just don't know where to send you for information, beyond the makers of the material itself.

-- Ed Huntress

This isn't PCD inserts he's looking for, however. It's vapor-deposited diamond coatings. They're a lot cheaper and a bit harder...although they're also a lot thinner.

Maybe they'll appear in a search for PCD but that isn't where I'd start.

-- Ed Huntress

Whoops, I should point out something else: The powder that will get in the air from either grinding or turning (amount unknown) could turn out to be VERY nasty, even highly toxic, stuff. You'd better do some checking. A lot of exotic materials that are harmless as solid pieces turn into skull-and-crossbones stuff when they're turned into fine particulates.

-- Ed Huntress

Ferrites are usually ground wet with diamond wheels. It's messy, but a diamond wheel can remove quite a bit of ferrite in a fairly short time.

Don, you mentioned using a diamond wheel. What would I use on my lathe to turn down the diameter? From experience so far, a sharp point turning insert does not work very well. Maybe I should try one of my larger radius inserts.

Do they have any type of diamond impregnated abrasive material I can use on a lathe? I am just throwing things out right now. I don't really know what else to try.

I will look at the McMaster diamond tips tools. But the magnets or so fragile, that if the tip of the tool catches any tiny imperfection, the magnet breaks.

Thanks for all the info.

Ceramic is much like glass. A hard brittle substance. I would grind it with a diamond wheel on a flexible shaft. Terry is on the right track. But, a wheel will be much faster.

Please note: I'm not a machinist, but I do know glass.

Randy Hansen SC Glass Tech. Scam Diego, Comi-fornia

learn from experience, unless you trip across someone else's account of how it's done -- from experience.

It's my experience that magnets really like to stick together. I haven't ground any so can't say if the average grinder would throw the dust hard enough though.

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

Some of the engineering ceramics are unbelievable.

Back when GE had a division working on making injection-molded, silicon-nitride turbocharger turbines (around 1980), they sent us editors a sample of the material, which was a stick around 4" long, 1/4" wide, and a little more than 3/16" thick. Silicon nitride is as hard as the hammers of hell and I expected it to be brittle. So I closed the door to my office, propped the stick up against the bottom of the door at a 45-deg. angle, and stomped on it with the heel of my shoe.

It dug a 1/2" gouge in my door. But it didn't break the first time. I really had to hit it very hard before it broke.

-- Ed Huntress

from

Yes and no. AlNiCo magnets are very easy to machine in any way you wish. NdFeB magnets are by nature very hard and brittle. Although they can be cut, drilled and machined, it should ONLY be done by folks who are experienced with ceramics. If the magnets get over about 300 deg F, they will lose their magnetism permanently. They are flammable, and it is not difficult while grinding or machining to get them (or the chips and dusts from cutting) so hot hot they ignite. If they do ignite, the fumes are toxic and the material burns very fast and hot, like Magnesium! In our experience any machining of these magnets should be done with diamond tools under lots of coolant with good ventilation and the risk of fire in mind.

I purchased the diamond tip turning bit from McMaster that Tim found. I will be here today. I'll give it another try. I am using lots of coolant. The tool and magnet never even get warm. As far as the dust. I would imagine the magnet would keep it down, as long as the coolant. But I will be more cautious of it.

Randy, not quite sure how I would use a diamond griding wheel on my lathe to turn down the diameter. I need to be accurate to a couple of thousands.

I tried machining some of those AlNiCo magnets last week. I think they were the AlNiCo 8 ones which had around 5% cobalt in them. That was a challenge. I wore out a solid cobalt drill bit, which barely put a dent in the magnet and a 3/16" solid carbide endmill which rounded the corners off only after a coulpe of passes.

As most can probably tell by now, I am pretty new to machining these things. But I am sure learning alot!

Thanks.

One thing you may now learn is that diamond-coated tools, or those tipped with a polycrystalline diamond compact, are not usually sharp unless you specificy that you want them sharp.

Anyhow, let us know how it works.

-- Ed Huntress