I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13 mm
25.4mm.

The strrength is not as important as the dimensions and that it be a solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets that I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim

"jim" wrote in message
...
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13
mm
25.4mm.

The strrength is not as important as the dimensions and that it be a solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at
least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets that
I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim


Why not mount a lot of smaller magnets in "parallel" ?

On Jul 27, 10:28am, jim wrote:
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13 mm
25.4mm.

The strrength is not as important as the dimensions and that it be a solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets that I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim

Jim, out of simple curiousity, what is your objection to the magnets
having holes in the middle?

Harry C.

"Cwatters" wrote in message
...

"jim" wrote in message
...
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13
mm
25.4mm.

The strrength is not as important as the dimensions and that it be a
solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their
strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at
least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets
that
I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim


Why not mount a lot of smaller magnets in "parallel" ?

The result would be many "hills" and "valleys" in the magnetic flux field.
That type of magnetic flux field is not desirable for this experiment.

On Jul 27, 9:28*am, jim wrote:
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. *The thickness can be as much as 13 mm
25.4mm.

The strrength is not as important as the dimensions and that it be a solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. *The magnets that I
have found generally top out at 76mm in diameter. *If I have missed
something in these searches, I would appreciate someone pointing it out.)

I suspect that you are asking the wrong question. I suspect that
your REAL question is, how can you create a close approximation
to a uniform magnetic field over an area of many square
centimeters.

The answer WON'T be by using a large monolithic hunk of ceramic.
Inevitable nonuniformities in manufacturing that arise during
the magetization step mean that the strength of field will vary
considerably between center and edge of the disc.

Instead, consider a large array of carefully matched magnets
faced off by pole pieces.

Why don't you share your actual requirements with us, rather
than trying to be so secretive about the experiment that you
intend to perform?

Jerry

wrote in message
...
On Jul 27, 10:28am, jim wrote:
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13
mm
25.4mm.

The strrength is not as important as the dimensions and that it be a
solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their
strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at
least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets that
I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim

Jim, out of simple curiousity, what is your objection to the magnets
having holes in the middle?

Harry C.

It alters the magetic flux field. I am looking for the same field as you
would "see" coming out of the end of a simple cylinder magnet.

jim

In article ,
says...

"Cwatters" wrote in message
...

"jim" wrote in message
...
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13
mm
25.4mm.

Probably a last resort or even off the wall but ...
I dont know if this is any help but I read somewhere last week about
a company that's produced a portable NMRI (battery powered no less) and
the photo I saw showed a round cylindrical device.

Being an MRI it must use magnets and (being so small they can't be
electro) since the shape is cylindrical it
just occurs to me they may have used just what you are asking for ...

If you contact them maybe they would be willing to connect you to their
source.

I think I saw it in Scientific American but I'm not too sure .. you may
have to google.

-peter-

On Jul 27, 10:28am, jim wrote:
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13 mm
25.4mm.

The strrength is not as important as the dimensions and that it be a solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets that I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim

Most large diameter ceramic magnets were designed/tooled for
loudspeakers and holding cup assemblies. Both of those involve large
quantities and require a hole, so they drive the market.

One option is to use a magnet fabricator to grind a disc shape out of
a solid rectangular block. There are standard 1" x 4" x 6" magnet
blocks (oriented thru the 1" direction). It won't be cheap because
it's a fair amount of labor to do that.

The other alternative is to weaken the Neodymium magnets since you
moderate heat. You'll have to experiment to find the right
temperature. If you get them too hot and demagnetize them too much,
you'll have to remag to restore them.

Good luck.

Mike

On Jul 27, 9:28am, jim wrote:
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13 mm
25.4mm.

The strrength is not as important as the dimensions and that it be a solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets that I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim

Mill a soft steel pole piece and affix a magnet or several magnets to
the back of that. The pole piece will spread and homogenize the field.

Why does it have to be a permanent magnet? Why aren't you considering
an air-core (or iron core) electromagnet?

PD

Mike D wrote:
On Jul 27, 10:28am, jim wrote:
I need some help in locating ceramic disc magnets that measure 120mm in
diameter with no hole in the center. The thickness can be as much as 13 mm
25.4mm.

The strrength is not as important as the dimensions and that it be a solid
disc (no hole in center).

I have found neo magnets that are up to 8" in diameter, but their strength
will actually make it more difficult to perform the initial experiment.

If anyone knows where I may purchase ceramic desci magnets that are at least
120mm in diameter and up to 25.4mm in thickness, with no holes in them,
please let me know.

Thank you for your help.

(I have Googled, Ask'd, Yahoo'd, etc. - all to no avail. The magnets that I
have found generally top out at 76mm in diameter. If I have missed
something in these searches, I would appreciate someone pointing it out.)

jim

Most large diameter ceramic magnets were designed/tooled for
loudspeakers and holding cup assemblies. Both of those involve large
quantities and require a hole, so they drive the market.

One option is to use a magnet fabricator to grind a disc shape out of
a solid rectangular block. There are standard 1" x 4" x 6" magnet
blocks (oriented thru the 1" direction). It won't be cheap because
it's a fair amount of labor to do that.

The other alternative is to weaken the Neodymium magnets since you
moderate heat. You'll have to experiment to find the right
temperature. If you get them too hot and demagnetize them too much,
you'll have to remag to restore them.

Good luck.

Mike

Thanks Mike.

I think I am going to retool my experiment to use a small neo magnet (3"
in diameter) for testing.

I had hoped to use something larger simply because working with larger
objects is easier than trying to machine all of the smaller parts that I
will need.

But, you work with what you have handy I guess.

jim