I have been attempting to turn down the diameter of some small ceramic
magnets. I have been using my regular carbide inserts and have not been
having much luck. I am flooding the magnet with water, and my lathe is
running at its highest rpms. I am only taking off about 1 to 2 thousands at
a time and turning my carriage very very slowly. I have successfully
managed to turn down 2 magnets so far, but have failed at about 8.
Basically, the magnets just crumble if I accidentally take off to much, or
twitch with my hand etc....

Is there a specific insert designed for turning ceramic, or are there any
special techniques that I haven't mentioned? Is there a recommended insert
radius for ceramic?

On my cnc mill, I designed a simple jig to securely hold the magnet. Using
a diamond coated 3/16" 4 flute end mill spinning at about 8000rpm with
coolant, I am able to machine down the thickness with no problems. I then
use a ceramic 1/4" drill bit to drill a hole down the center, again with no
problems. But when it comes to turning down the diameter I just can't do it
with the tools I have.

Thanks for any info. I am hoping to succeed in this final machining
operation.

"Terry G" wrote in message
news:6UYSd.80843$Yu.64019@fed1read01...
I have been attempting to turn down the diameter of some small ceramic
magnets. I have been using my regular carbide inserts and have not been
having much luck. I am flooding the magnet with water, and my lathe is
running at its highest rpms. I am only taking off about 1 to 2 thousands
at
a time and turning my carriage very very slowly. I have successfully
managed to turn down 2 magnets so far, but have failed at about 8.
Basically, the magnets just crumble if I accidentally take off to much, or
twitch with my hand etc....

Is there a specific insert designed for turning ceramic, or are there any
special techniques that I haven't mentioned? Is there a recommended
insert
radius for ceramic?

On my cnc mill, I designed a simple jig to securely hold the magnet.
Using
a diamond coated 3/16" 4 flute end mill spinning at about 8000rpm with
coolant, I am able to machine down the thickness with no problems. I then
use a ceramic 1/4" drill bit to drill a hole down the center, again with
no
problems. But when it comes to turning down the diameter I just can't do
it
with the tools I have.

Thanks for any info. I am hoping to succeed in this final machining
operation.




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

"Terry" wrote in message
ps.com...
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.

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

"Terry" wrote in message
oups.com...
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.

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 @ http://webpages.charter.net/dawill/tmoranwms

Terry wrote:

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.

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.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

"Terry" wrote in message
oups.com...
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.

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?


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.

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 g, 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

"Terry" wrote in message
oups.com...
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

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

"Terry" wrote in message
oups.com...
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


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

On Wed, 23 Feb 2005 12:48:54 -0500, "Ed Huntress"
wrote:

"Terry" wrote in message
ups.com...
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.

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

Search term "PCD Inserts"

Gunner

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

"Gunner" wrote in message
...
On Wed, 23 Feb 2005 12:48:54 -0500, "Ed Huntress"
wrote:

"Terry" wrote in message
ups.com...
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.

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

Search term "PCD Inserts"

Gunner

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

On Wed, 23 Feb 2005 02:27:14 -0800, "Terry G"
wrote:

I have been attempting to turn down the diameter of some small ceramic
magnets. I have been using my regular carbide inserts and have not been
having much luck. I am flooding the magnet with water, and my lathe is
running at its highest rpms. I am only taking off about 1 to 2 thousands at
a time and turning my carriage very very slowly. I have successfully
managed to turn down 2 magnets so far, but have failed at about 8.
Basically, the magnets just crumble if I accidentally take off to much, or
twitch with my hand etc....

Is there a specific insert designed for turning ceramic, or are there any
special techniques that I haven't mentioned? Is there a recommended insert
radius for ceramic?

On my cnc mill, I designed a simple jig to securely hold the magnet. Using
a diamond coated 3/16" 4 flute end mill spinning at about 8000rpm with
coolant, I am able to machine down the thickness with no problems. I then
use a ceramic 1/4" drill bit to drill a hole down the center, again with no
problems. But when it comes to turning down the diameter I just can't do it
with the tools I have.

Thanks for any info. I am hoping to succeed in this final machining
operation.

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.

On 23 Feb 2005 14:09:50 -0800, "Terry" wrote:

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.

On 23 Feb 2005 14:09:50 -0800, "Terry" wrote:

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 would think of it more as a grinding or abrasion operation than as
turning. I don't think I'd do it in a lathe because I wouldn't want
that abrasive mess near it. The little ferrite machining I've done
has been freehand with diamond burrs in a Dremel or diegrinder.

You might use a 1/4" shaft diamond "burr" or even a diamond wheel in
your mill. For wheels, see
http://www.cyberrockhound.com/grinding_wheels.htm
Set up a spin index or rotary table, mount the workpiece to that, and
advance the work toward the spinning burr by moving the mill table.
Rotate the work 360 by hand, advance another coupla thou and do it
again, and so on. If I had a lot of them to do, I might rig up a
slo-syn motor to the crank of the rotary table.

On Wed, 23 Feb 2005 02:27:14 -0800, "Terry G"
wrote:

I have been attempting to turn down the diameter of some small ceramic
magnets. I have been using my regular carbide inserts and have not been
having much luck.

You will use a diamond post grinder. Single point diamond turning will
be too slow for that diameter reduction and will still chip the
material.
But the good new is that a foredom handpiece will fit many Phase II
boring bar holders, and sintered bronze or even plated type diamond
shank-mounted wheels are cheap and available a lot of places.
You will not be able to observe the surface while you are machining
(wet) because the magnet itself will hold the particles, so will be
coated with black gunk.
(I once worked at an optics company. We routinely edged exotic
materials to round blanks: Sapphire, various ceramics and
glass/ceramics, etc.)