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View Full Version : Can a "single", spherical ball bearing be permanently magnetized?



rigney
2010-Jun-28, 11:31 PM
I've been to several web sites and asked the question. Can a "Single" spherical ball bearing be permanently magnetized? I know that one can be picked up with a magnet, but no residual magnetism remains after separation. Would appreciate any and all input.

swampyankee
2010-Jun-28, 11:38 PM
Why not? Presuming it's made out of a ferromagnetic material, there should be no reason it can't be. If your question is "can a single spherical ball from a bearing be magnetized without the others being magnetized?" I'd answer that it would be quite unlikely; unlikely enough so that I would conclude that the ball was magnetized before it was installed into the bearing.

Of course, not all balls used in bearings are ferromagnetic; some are, for example, ceramic (SiN, I believe)

rigney
2010-Jun-29, 01:32 AM
Let me rephrase the question. Can a "single" ferrous and spherical ball bearing, either iron or steel, be magnetized with any permanence?

01101001
2010-Jun-29, 01:46 AM
Let me rephrase the question. Can a "single" ferrous and spherical ball bearing, either iron or steel, be magnetized with any permanence?

Yes.

rigney
2010-Jun-29, 01:54 AM
Would you explain your position on my question. I'm afraid yes just doesn't do it for me, or any other civil minded person looking for an answer.

Swift
2010-Jun-29, 02:09 AM
Let me rephrase the question. Can a "single" ferrous and spherical ball bearing, either iron or steel, be magnetized with any permanence?
Yes (I don't know why you think that an uncivil answer).

Why is single in quotes? There is nothing magical about being a ball bearing other than it is round and smooth. If it is made of the right type of steel (there are types than can not be magnetized), it is below the Curie temperature, and you put it in a big enough magnetic field, it can be magnetized, as easily as a steel nail or any other piece of steel.

Squink
2010-Jun-29, 02:12 AM
NEODYMIUM SPHERE MAGNETS (http://www.kjmagnetics.com/products.asp?cat=12)

ravens_cry
2010-Jun-29, 02:30 AM
My guess is they are wondering about the magnetic poles on such a magnet. Well ,the Earth is a magnet, and it has it's poles at points near the north and south geographic pole.

01101001
2010-Jun-29, 02:37 AM
Would you explain your position on my question. I'm afraid yes just doesn't do it for me, or any other civil minded person looking for an answer.

Yes. It means yes. The answer to your question is yes. Some metallic spheres which function as bearings can be magnetized.

Yes. Very civilly yes.

Nowhere Man
2010-Jun-29, 02:45 AM
Why stop at one? Try 216. It's a wonderful fidget to fiddle with.

http://www.getbuckyballs.com

Fred

Jens
2010-Jun-29, 04:40 AM
Let me rephrase the question. Can a "single" ferrous and spherical ball bearing, either iron or steel, be magnetized with any permanence?

Not an answer, but a question about the question. If objects can be magnetized, then why do you thing there is anything special about a ball bearing that would make it impossible? Because of the shape, or the size? Or because it is single? Why is there any difference between one ball bearing and say two ball bearings?

Jeff Root
2010-Jun-29, 06:17 AM
I think ravens_cry got it. Two spherical ball bearings touching each
other makes a linear shape which could obviously contain a magnetic
dipole, with one pole at each end, so rigney isn't perplexed by such
a configuration as he is by the mystery of how a symmetrical sphere
of magnetic material could contain a magnetic dipole. The answer
to his question then is: The shape is irrelevant. The ability of the
atoms to line up and stay lined up is all that matters. The atoms
are "lined up" when some of their electron clouds are oriented in
the same way rather than in random directions.

Making the magnet a particular shape causes the resulting magnetic
field to also have a particular shape, which is almost always useful.
Typically a magnet is shaped to concentrate the field in a small area
of the magnet's surface so that the force it applies will be strongest
in that area.

I have some rectilinear magnets approximately 1 cm x 2 cm x 5 cm.
You might guess that the magnetic field would run the length of the
magnets, with the poles at the far ends. But the poles are actually
on the broad faces instead. The magnetic field runs through the
magnets in the shortest dimension instead of the longest, the way
it does in a familiar bar magnet.

-- Jeff, in Minneapolis

rigney
2010-Jun-29, 01:04 PM
I think ravens_cry got it. Two spherical ball bearings touching each
other makes a linear shape which could obviously contain a magnetic
dipole, with one pole at each end, so rigney isn't perplexed by such
a configuration as he is by the mystery of how a symmetrical sphere
of magnetic material could contain a magnetic dipole. The answer
to his question then is: The shape is irrelevant. The ability of the
atoms to line up and stay lined up is all that matters. The atoms
are "lined up" when some of their electron clouds are oriented in
the same way rather than in random directions.

Making the magnet a particular shape causes the resulting magnetic
field to also have a particular shape, which is almost always useful.
Typically a magnet is shaped to concentrate the field in a small area
of the magnet's surface so that the force it applies will be strongest
in that area.

I have some rectilinear magnets approximately 1 cm x 2 cm x 5 cm.
You might guess that the magnetic field would run the length of the
magnets, with the poles at the far ends. But the poles are actually
on the broad faces instead. The magnetic field runs through the
magnets in the shortest dimension instead of the longest, the way
it does in a familiar bar magnet.

-- Jeff, in Minneapolis

Thanks Jeff, some of you guys are pretty thoughtful. I'm not into science that much other than being slightly inquisitive. From what I've read about rare earth (neodymium) magnets, is that while they are very powerful, they are not a natural phenomena; but put together in an isotopic manner that builds this power into them. Permanency was also a factor. While an iron or steel spherical bearing can be shocked into believing it's a magnet for a while, the life as one is short lived. Even the strength of an istopic magnet fades over time, but not nearly as quick as one made from iron or steel. And heat, beyond anything that might burn your hand, pretty much kills either of them. The reason I even brought up the visual of a ball bearing is that I believe each atom is endowed with monopoles and on a lesser scale, might resemble something similar to a spherical ball bearing after being magnetised. Guess I was wrong, but thanks again.

Swift
2010-Jun-29, 01:23 PM
While an iron or steel spherical bearing can be shocked into believing it's a magnet for a while, the life as one is short lived. Even the strength of an istopic magnet fades over time, but not nearly as quick as one made from iron or steel. And heat, beyond anything that might burn your hand, pretty much kills either of them.
No, iron or steel can be "permanently" magnetized. Permanent is in quotes, because there are conditions that can demagnetize any material. As you said, heating is one of them. There is a characteristic of a magnetic material called the Curie Temperature. If you heat a magnetic above that temperature, there is enough thermal energy in the material to randomize the spin directions of the individual atoms and demagnetize the material.

From the wikipedia article on Curie temperature (http://en.wikipedia.org/wiki/Curie_temperature), here are some typical values (well above hand burning temperatures):

Iron (Fe) 768C.
Cobalt (Co) 1150C.
Nickel (Ni) 360C.
Iron Oxide (Fe2O3) 622C.

There are naturally occurring iron ore deposits in the Earth that are still magnetized as they were by the Earth's magnetic field, in the direction that field pointed at the time they were formed (magnetic banding as evidence of plate tectonics (http://www.geologyrocks.co.uk/tutorials/plate_tectonics_evidence)).

jlhredshift
2010-Jun-29, 01:41 PM
No, iron or steel can be "permanently" magnetized. Permanent is in quotes, because there are conditions that can demagnetize any material. As you said, heating is one of them. There is a characteristic of a magnetic material called the Curie Temperature. If you heat a magnetic above that temperature, there is enough thermal energy in the material to randomize the spin directions of the individual atoms and demagnetize the material.

From the wikipedia article on Curie temperature (http://en.wikipedia.org/wiki/Curie_temperature), here are some typical values (well above hand burning temperatures):

Iron (Fe) 768C.
Cobalt (Co) 1150C.
Nickel (Ni) 360C.
Iron Oxide (Fe2O3) 622C.

There are naturally occurring iron ore deposits in the Earth that are still magnetized as they were by the Earth's magnetic field, in the direction that field pointed at the time they were formed (magnetic banding as evidence of plate tectonics (http://www.geologyrocks.co.uk/tutorials/plate_tectonics_evidence)).

Igneous rocks do the best job of preserving the paleomagnetic field, but certain sedimentary rocks can do so as well.

HenrikOlsen
2010-Jun-29, 08:01 PM
Thanks Jeff, some of you guys are pretty thoughtful. I'm not into science that much other than being slightly inquisitive. From what I've read about rare earth (neodymium) magnets, is that while they are very powerful, they are not a natural phenomena; but put together in an isotopic manner that builds this power into them.
Nope, when they are first made, sintered in an oven really as they are ceramic like, they have no inherent magnetism apart from the very feint one from the earths magnetic field locked in as they cooled.
They are then magnetized using a very powerful electromagnet, just like a steel "permanent" magnet is made.

The only difference is the amount of magnetic field that the material can hold per volume.

The bit that may be confusing is that there are several stainless steels that are not ferromagnetic and will thus neither be attracted by a magnet nor be magnetized if held in a strong magnetic field and if you've been playing with stainless steel balls and a magnet you may have become confused about the reason for the lack of magnetism, it wouldn't have been because of the shape but because of the material.

Jeff Root
2010-Jun-29, 09:14 PM
I don't recall ever coming across a stainless steel sphere. The two
loose (and rather large) solid steel spheres I found just now are both
magnetic. My kitchen sink is nonmagnetic stainless, though it has
some kind of magnetic frame hidden underneath the edge. Some of
my tableware is magnetic and some is not. One pattern has magnetic
stainless table knives but nonmagnetic forks and spoons, which I think
are silver-plated stainless steel.

-- Jeff, in Minneapolis

Swift
2010-Jun-29, 09:24 PM
I don't recall ever coming across a stainless steel sphere.
Steel spheres for sale (http://www.steelmedia.com/steel-balls.htm)
Your choice of stainless (AISI 304, 316, etc.), chrome, or high carbon. 1mm up to 12.5 mm

neilzero
2010-Jun-30, 02:09 AM
The alloy typically used to make ball bearings is different than the best alloys for permanent magnets, however my guess is a usefully strong magnet can be made and will lose less than half its strength per year = likely qualifies as a permanent. A keeper for the magnetized ball baring might retain half the magnetism for a century. I don't think the spherical shape much inhibits it being magnetized. A sharp blow to the ball bearing while in a strong magnetic field may help magnetize the ball bearing. Spheres made of non-magnetic material cannot be magnetized, but that would be rare for ball bearings, unless the manufacture desired early failure = plan obsolescence. Neil

sabianq
2010-Jun-30, 02:18 AM
like this?
"Powerful 3/8" diameter rare-earth neodymium magnetic sphere. Shiny, plated finish. Because of its high strength, use caution when handling around metal objects or other magnets. Also available in 3/16", 1/4", 1/2" and 1" diameter."

http://www.allelectronics.com/make-a-store/item/MAG-105/3/8-SPHERICAL-NEODYMIUM-MAGNET/1.html

mugaliens
2010-Jun-30, 08:48 AM
I wonder if there's an optimum size for removing ferrous intestinal metals...

clop
2010-Jun-30, 09:52 AM
I think ravens_cry got it. Two spherical ball bearings touching each
other makes a linear shape which could obviously contain a magnetic
dipole, with one pole at each end, so rigney isn't perplexed by such
a configuration as he is by the mystery of how a symmetrical sphere
of magnetic material could contain a magnetic dipole. The answer
to his question then is: The shape is irrelevant. The ability of the
atoms to line up and stay lined up is all that matters. The atoms
are "lined up" when some of their electron clouds are oriented in
the same way rather than in random directions.

Making the magnet a particular shape causes the resulting magnetic
field to also have a particular shape, which is almost always useful.
Typically a magnet is shaped to concentrate the field in a small area
of the magnet's surface so that the force it applies will be strongest
in that area.

I have some rectilinear magnets approximately 1 cm x 2 cm x 5 cm.
You might guess that the magnetic field would run the length of the
magnets, with the poles at the far ends. But the poles are actually
on the broad faces instead. The magnetic field runs through the
magnets in the shortest dimension instead of the longest, the way
it does in a familiar bar magnet.

-- Jeff, in Minneapolis

Hey Jeff, why do your posts always appear on my screen narrowed to around 50 characters wide? You're the only one who appears this way, and you've always done it!

clop

captain swoop
2010-Jun-30, 12:07 PM
Same on my screen

HenrikOlsen
2010-Jun-30, 12:22 PM
He makes the linefeeds
himself instead of
relying on the
browser to
do it for
him.

It could
be the result
of writing the posts
in another editor before
copy/pasting them over, but
I can't remember any mention of
him doing so in any previous posts.

rigney
2010-Jun-30, 02:42 PM
I wonder if there's an optimum size for removing ferrous intestinal metals...
Teddy was like that. Fine Roosevelt, and quite a guy! Undaunted and precarious. Can't short change him on that, but he only forgot one thing:

Into this life we are let, first only asking; then to our fame
Oh! so quickly do we leave, taking not; but as we came.

Gray twilight is a beautiful setting, if someone walks with you.

rigney
2010-Jun-30, 02:57 PM
I wonder if there's an optimum size for removing ferrous intestinal metals...

Teddy was like that. Fine Roosevelt, and quite a guy! Undaunted and precarious. Can't short change him on that, but he only forgot one thing:

Into this life we are let, first only asking; then to our fame
Oh! so quickly do we leave, taking not; but as we came.

Gray twilight is a beautiful setting, if someone walks with you.

Trebuchet
2010-Jun-30, 05:42 PM
I have a couple of spherical hematite magnets, sold as a novelty somewhere or other. Harbor Freight Tools, I think. They came with some elongated ones, which if I recall correctly are polarized across the short axis, not the long way as you'd expect. You can toss them in the air separately and they'll fly together with a loud clack. So I can't see any reason you can't have a spherical steel magnet. You wouldn't want them in a bearing of course, it would kind of defeat the purpose.

And as a mechanical engineer, I cringe at the use of the term "ball bearing" to refer to a single ball. A ball bearing is the whole bearing with an inner and outer race and a number of balls. The individual balls would be "bearing balls", not ball bearings. Also note that bearing balls are frequently high hardness varieties of stainless and may be much less magnetic than carbon steel.

Swift
2010-Jun-30, 07:22 PM
Hey Jeff, why do your posts always appear on my screen narrowed to around 50 characters wide? You're the only one who appears this way, and you've always done it!

clop
Actually, he is not, there are a couple of posters that have this. I don't know about Jeff, but it is often to do with the particulars of the browser or their network.

Now, let's get back on topic

Swift
2010-Jun-30, 07:24 PM
I wonder if there's an optimum size for removing ferrous intestinal metals...
Are you referrring to cow magnets (http://en.wikipedia.org/wiki/Cow_magnet)? I suspect their optimum size is determined by the diameter of a cow's gut.

rigney
2010-Jun-30, 08:00 PM
I have a couple of spherical hematite magnets, sold as a novelty somewhere or other. Harbor Freight Tools, I think. They came with some elongated ones, which if I recall correctly are polarized across the short axis, not the long way as you'd expect. You can toss them in the air separately and they'll fly together with a loud clack. So I can't see any reason you can't have a spherical steel magnet. You wouldn't want them in a bearing of course, it would kind of defeat the purpose.

And as a mechanical engineer, I cringe at the use of the term "ball bearing" to refer to a single ball. A ball bearing is the whole bearing with an inner and outer race and a number of balls. The individual balls would be "bearing balls", not ball bearings. Also note that bearing balls are frequently high hardness varieties of stainless and may be much less magnetic than carbon steel.

The Trebuchet? Me, I have a penchant for 357s, 45s, 9mms and 306s. Throwing rocks just doesen't seem do it anymore. Worked with bearings all my life and never once made that dinstiction. Good correction. Thanks

swampyankee
2010-Jun-30, 08:35 PM
And as a mechanical engineer, I cringe at the use of the term "ball bearing" to refer to a single ball. A ball bearing is the whole bearing with an inner and outer race and a number of balls. The individual balls would be "bearing balls", not ball bearings. Also note that bearing balls are frequently high hardness varieties of stainless and may be much less magnetic than carbon steel.

Also a mechanical engineer. Thank you.

rigney
2010-Jul-01, 01:25 AM
Are you referrring to cow magnets (http://en.wikipedia.org/wiki/Cow_magnet)? I suspect their optimum size is determined by the diameter of a cow's gut.

Depends on which end of "You" that "you", might want to try the experiment on? But then, you're not a cow, or are you?

dgh64
2010-Jul-02, 06:07 PM
Um, did you read the linked article? Cow magnets go in the animal's mouth. They settle in the first or second stomach and collect bits of metal that the cow eats. I don't think they're ever used on the, uh, other end.

I'm trying to imagine a bearing in which each ball is a magnet, and they're all trying to roll but they keep being attracted/repelled by the ones next to them. Eventually they'd end up with their North ends all pointing to the next in a circle, sliding instead of rolling (unless the magnetization was pretty weak). Not sure why you'd want to do this.