Confused by a magnet

[Michael GilliganParticipant @michaelgilligan61133]

Browsing ebay last night, I spotted that Zoro is listing Eclipse Magnetics E1001/NEO at what appears reasonable price … but I’m confused by the product itself.

Farnell has the Eclipse data-sheet available: **LINK**

https://www.farnell.com/datasheets/2290329.pdf

… but I’m still confused.

Does the Zinc plated casing provide any useful functionality, or is it just a cheap way of making a small magnet look bigger ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

[John HaineParticipant @johnhaine32865]

Virtue out of necessity I think. Usually they are plated with nickel, then copper then nickel I think as otherwise the material corrodes very quickly. Zinc is probably cheaper?

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, John … but it appears to be a casing rather than just a plating-job

MichaelG.

[DiogenesIIParticipant @diogenesii]

Perhaps a countersunk fixing could cause an unconstrained magnet to split if carelessly fixed.. ..is the housing to provide support..? 'containment'

Edited By DiogenesII on 18/12/2022 08:24:11

[David Davies 8Participant @daviddavies8]

Hi Michael,

I believe the”can” is there to complete the magnetic circuit. Once the “target” touches the face of the magnet a path exists for the magnetic flux to complete its circuit. For this to be so the “target” needs to be of sufficient diameter and aligned correctly to cover the can and magnet.

HTH

Dave

[Kiwi BlokeParticipant @kiwibloke62605]

Neodymium is too brittle, fragile and chemically 'active' to be used 'naked'. Hence the magnets are encased for mechanical and chemical protection, and the Zn plate is presumably to protect the case material against corrosion. It looks like the case also acts as a 'pot' magnet's peripheral pole piece, as suggested in the post above.

Edited By Kiwi Bloke on 18/12/2022 08:54:03

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, folks

That seems to make sense … now I’m just surprised to see how many ‘naked’ ones are around.

I suppose if anyone is going to do things right, it should be Eclipse

MichaelG.

.

Edit: __ I’ve just ordered three, at Zoro’s attractive price.

Edited By Michael Gilligan on 18/12/2022 09:14:41

[John HaineParticipant @johnhaine32865]

I think that neodymium nudity is very rare – every one I've ever seen is nickel plated at least. Once I managed to chip the coating off and the magnet quickly corroded.

**LINK** shows a pot magnet that definitely has a surrounding case – however you can clearly see the gap between the "pot" and the centre pole needed to make sure the flux isn't shorted. There is only a very thin line between the outside "pot" and the magnet face in the Eclipse photo though – but I notice that if you look at the screw hole it does look as if there's a plate at the bottom. You must tell us what you find Michael!

[HopperParticipant @hopper]

From the dreaded Wiki:

Sintered Nd₂Fe₁₄B [Neodymium] tends to be vulnerable to corrosion, especially along grain boundaries of a sintered magnet. This type of corrosion can cause serious deterioration, including crumbling of a magnet into a powder of small magnetic particles, or spalling of a surface layer.

This vulnerability is addressed in many commercial products by adding a protective coating to prevent exposure to the atmosphere. Nickel, nickel-copper-nickel and zinc platings are the standard methods, although plating with other metals, or polymer and lacquer protective coatings, are also in use.^[21]

^And

Magnets that get too near each other can strike each other with enough force to chip and shatter the brittle magnets, and the flying chips can cause various injuries, especially eye injuries.

So apart from corrosion and crumbling resistance, I guess if the posted countersunk variety were used naked in a contact situation, such as a cupboard door closer etc, the impact could shatter it without the zinc-plated envelope to hold it together.

[Jon LawesParticipant @jonlawes51698]

Those Neodym magnets can really shatter into quite sharp shards.

[Ady1Participant @ady1]

I've used the ebay 10mm ones over the years and they are extremely fragile

If you look at them the wrong way they break in half, but they still work fine

Edited By Ady1 on 18/12/2022 10:59:38

[Tim StevensParticipant @timstevens64731]

I agree with Ady 1 that Neo magnets from a well known web source are both fragile and rust prone once they are cracked. And some of them arrive like that – but they still work for attaching important (but temporary) papers to a tool box lid or the top of a mill column.

I suspect that as the Neo mix is chosen solely for its magnetic properties, it is not easy to form into shape by old-style methods. My guess is that sintering is used, and a quick flash of zinc is a good way to stop the rust while not affecting the dimensions significantly.

I await news from Michael G about what his magnets comprise when they arrive. If they arrive.

Cheers, Tim

[peak4Participant @peak4]

Re Corrosion, see P92 of the eclipse Magnets & Magnetic Tools catalogue available for download from HERE
https://www.eclipsemagnetics.com/resources/?filter_related_product_type=2403&filter_resource_type=2398#resources

A very useful source of larger flat magnets, attached to a backing plate is redundant computer hard disk drives; there's two in each single platter drive.

Bill

Edited By peak4 on 18/12/2022 11:23:34

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Haine on 18/12/2022 10:11:35:

I think that neodymium nudity is very rare – every one I've ever seen is nickel plated at least. […]

[…]

You must tell us what you find Michael!

.

Sorry, John … cross-purposes … l was thinking more in terms of wearing [or not wearing] a jacket, rather than ‘body-painting’ 

Yes, I will happily report on my purchase.

MichaelG.

Edited By Michael Gilligan on 18/12/2022 11:35:50

[Robert Atkinson 2Participant @robertatkinson2]

David Davies 8 is correct, the casing or "pot" is there to complete the magnetic circuit and increase the force. They are often called Pot magnets and existed before rare earth magnets.
The pot also protects a brittle magnet from direct impacts as a secondary benefit. Both magnet and pot are plated to prevent corrosion.

https://www.stanfordmagnets.com/what-are-the-types-of-pot-magnets.html

Robert G8RPI.

[Andrew TinsleyParticipant @andrewtinsley63637]

I looked up the magnets on the Zoro website. It describes the plating system and the reason why they are plated. Namely to protect against corrosion.

Andrew.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Andrew Tinsley on 18/12/2022 12:42:50:

I looked up the magnets on the Zoro website. It describes the plating system and the reason why they are plated. Namely to protect against corrosion.

Andrew.

.

So did I, Andrew … my question was why there was a can around something which is commonly supplied ‘naked’ but plated.

MichaelG.

[peak4Participant @peak4]

Posted by Michael Gilligan on 18/12/2022 14:53:11:

Posted by Andrew Tinsley on 18/12/2022 12:42:50:

I looked up the magnets on the Zoro website. It describes the plating system and the reason why they are plated. Namely to protect against corrosion.

Andrew.

.

So did I, Andrew … my question was why there was a can around something which is commonly supplied ‘naked’ but plated.

MichaelG.

See P93 of the catalogue I linked to in an earlier post, as well as Robert's link.

Bill

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Bill

Sorry … I didn’t intend to revive the discussion by replying to Andrew

Having already looked at P93 and the other references, I was happy that my question had been answered.

When they arrive [at £1.75 each, post free] I will take a photo to better illustrate the construction.

MichaelG.

[Anonymous]

Lee Valley have been selling similar arrangements for years and have a somewhat explanation here.

 

(LV used to have such a nice, simple website with quite a lot of general background info pages – now it seems to have gone over to "Modern Busy" and if the background is still there, I don't have time to find it.)

Edited By Peter Greene 🇨🇦 on 18/12/2022 19:34:27

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Peter Greene 🇨🇦 on 18/12/2022 19:28:54:

Lee Valley have been selling similar arrangements for years and have a somewhat explanation here.

[…]

.

Interesting to see the component parts shown separately, Peter

Unless my eyes are deceiving me, that’s a somewhat different configuration to the Eclipse offering.

.

.

We shall see … hopefully soon, but who knows ?

MichaelG.

Edited By Michael Gilligan on 18/12/2022 20:52:19

[Anonymous]

Yes … it seems the Eclipse one has a countersunk magnet. Don't really know why that's necessary and it makes the magnet a bit "special".

[Robert Atkinson 2Participant @robertatkinson2]

The Lee Valley design uses a standard magnet but has the disadvantage that the mggnet fits over the screw after fixing. This has two disabvantages:

1. The assenbly is thicker / taller

2. It is very difficult to remove the maget to get at the screw if it needs tightening or the assembly moving.

Robert G8RPI.

[noel shelleyParticipant @noelshelley55608]

As an aside to all of this , when salvaging speaker magnets I PART THE FRONT AND BACK PLATES, grind any rivet heads Etc off, clean up, wrap the centre core in tape to fill the coil gap and reassemble. This keeps magnetic dust Etc from bridging the gap and weakening the field. BUT if the magnet is large BE VERY CAREFUL ! When placing on an iron or steel table that you have NOT got the tips of your fingers in the gap, it WILL hurt ! Great for mounting lamps Etc Noel.

[Author]

Posts