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**David Schwab** · 01-23-2007, 03:46 PM

Originally posted by Magnetosaure View Post

Plus the Stew-Mac covers, that are 1-15/16", are not magnetically transparent... So not Nickel Silver

I'm just curious... how are they not "magnetically transparent"?

I know we've all decided that we prefer the tone of nickel silver to brass, but neither interferes with the magnetic field directly since they aren't ferrous metals.
It's really about the conductivity of the cover and eddy currents that flow on the surface.
Also nickel silver is a form of white brass, so I'm wondering how different they really are as far as conductivity.

Now if one cover is thicker than another, that would make a difference. Also if they are plated, which they all are, having a thin copper layer might make a difference.

**Magnetosaure** · 01-23-2007, 04:20 PM

Maybe I used a wrong term...

When you approach a Stew-Mac cover to a strong magnet, well, it is attracted enough to get stuck to it (weakly, but...) Wich is not the case with for example the Seymour Duncan Antiquity cover that I'm supposed to change (That's why I need 1-15/16" spacing covers!)

That's what I call not being "transparent". For me transparent would mean not being attracted. I admit I can be wrong with the use of that term.

**David Schwab** · 01-23-2007, 04:41 PM

Well if the cover is magnetic, that's not a good thing!

Be aware however that non ferrous metals will exhibit some degree of repulsion to a strong magnet.. the larger the piece of metal the more you will feel it. But they wont stick to it.

**David King** · 01-23-2007, 07:05 PM

I'd just like to point out that nickel, cobalt and iron are all ferro-magnetic elements. Nickel is the least ferro-magnetic of the three and alloying it to other metals probably has some effect on it's magnetic properties. After all AlNiCo is a pretty good indication that alloys containing Nickel have the potential to have magnetic properties.

**Magnetosaure** · 01-23-2007, 07:16 PM

VERY good point, David!

**David Schwab** · 01-23-2007, 09:53 PM

David, you brought up a very interesting point indeed. I hadn't thought about this, but Nickel is one of the ferro-magnetic elements (manganese, nickel, chromium, iron and cobalt), and the only reason nickel coils aren't magnetic is because they are mostly copper. But then so is nickel silver (Alloy No.752 is 65% copper, 18% nickel, 17% zinc).

On the other hand, brass is just copper and zinc... not magnetic at all.

Hmmmmmm.....

**soundmasterg** · 01-23-2007, 11:36 PM

Whats the problem with the Duncan cover on the Antiquity? Most of the stuff I've seen from Seymour's product line looks to be pretty vintage accurate unless something has changed within the last couple years.

**Possum** · 01-24-2007, 03:35 AM

something wrong here....

You shouldn't be getting ANY magnet pull from any pickup cover, are you testing the cover by itself with nothing in it? I have a big ass neodymium magnet I used to charge magnets with and taking a nickel silver and a brass cover up to it, it doesn't pull at all. If there was anything to pull it surely would do it, this thing is strong. If you're sliding the cover across a magnet it will generate eddy currents and drag on the metal but it will do this to ANY metal, so this is not a valid test and is not magnet pull, it is eddy currents generated in a conductive metal. If you have a dremel sand down a small area inside the cover, you should not be seeing ANY brass there, you may see some copper plating is all. If they are brass they are crap. their website says they are chrome plated, this isn't good either, I've only seen chrome on brass covers, not on nickel silver....

**Magnetosaure** · 01-24-2007, 10:45 AM

Well, I've done the test again with another Gold plated cover from Stew-Mac, with nothing in it of course, and it does stuck to the neodymium magnet. I just approach the cover to the magnet until it's in contact, I don't slide it on the magnet, and it stays in place!

Is it because it's gold plated?

This "test" doesn't produce the same result with the SD cover, wich DOESN'T stick to the magnet. A good sign indeed

Gold plated Stew-Mac covers are made by Schaller. And it looks like they're made of Brass...

BTW, even their Tele Neck covers (chrome plated) DO have a "reaction" when approached to the neodymium magnet...

**Joe Gwinn** · 01-24-2007, 01:42 PM

Originally posted by Magnetosaure View Post

Well, I've done the test again with another Gold plated cover from Stew-Mac, with nothing in it of course, and it does stick to the neodymium magnet. I just approach the cover to the magnet until it's in contact, I don't slide it on the magnet, and it stays in place!

Is it because it's gold plated?

This "test" doesn't produce the same result with the SD cover, which DOESN'T stick to the magnet. A good sign indeed

Gold plated Stew-Mac covers are made by Schaller. And it looks like they're made of Brass...

BTW, even their Tele Neck covers (chrome plated) DO have a "reaction" when approached to the neodymium magnet...

How strong is the magnetic pull, compared to a piece of thin mild steel sheet? From the above, I get the impression that the pull is weak, but nonetheless (just) enough to make the magnet stick.

Anyway, some kinds of stainless steel (like 18/10 alloy) become weakly magnetic when mechanically worked. Deep drawing, such as that needed to form a cover from a flat sheet, would suffice.

Does the magnetic pull vary with position on the cover? The center of the top is likely to have suffered less mechanical working (stretching) than the sides, although covers are small enough that this effect may not be pronounced.

Gold plating has no effect on magnetic properties whatsoever.

**Magnetosaure** · 01-24-2007, 02:23 PM

Well, the magnetic pull is weak, nothing compare to, say, a HB steel spacer, but enough to make the cover stick to it when you hold the magnet parrallel to the ground.

I remember now having found the same thing on a mid 90's Gibson HB gold cover.

The pull seems even on all the surface of the cover, top center and sides.

The magnet I use for this test is just a 1x1/2 inches neodymium cylindre. Not a VERY VERY strong magnet in fact...

**David King** · 01-24-2007, 10:54 PM

Gold plating usually goes over a copper base plating. Had there been a layer of pure nickel plating under there it would account for the magnetic pull. Could it be that all the covers are getting nickel plate first?
Plating over stainless doesn't seem practical but it may be possible.

**Joe Gwinn** · 01-25-2007, 02:42 PM

Originally posted by David King View Post

Gold plating usually goes over a copper base plating. Had there been a layer of pure nickel plating under there it would account for the magnetic pull. Could it be that all the covers are getting nickel plate first?
Plating over stainless doesn't seem practical but it may be possible.

A thin layer of nickel under the gold could also explain the effect.

One can certainly gold plate stainless (which has high nickel content). The economic reason to do so is that it's cheaper to make all the covers from one set of tooling and in one big run, and then goldplate only those for which there are orders. The metal in the covers just isn't worth all that much, even if it is stainless, so a special run isn't justified. Nor is tooling intended for steel necessarily going to work well on nickel silver, and vice versa. (They may, but it isn't automatic.)

Easy way to tell if it's steel versus brass or nickel silver is to file a corner - steels feel quite different than brasses when filed.

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