does anybody know what, exactly, "coin silver" is (I found something
like 90% silver 10% copper, but are there other standards), and what its
mechanical properties are?
I'm looking for a replacement/alternative alloy for CuSn6 for
low-temperature, non-magnetic applications.
I thought 'coin silver' had a lot of nickel in it.
You might want to talk to a low-temperature engineer who's had
experiences with non-magnetic materials. If you need something
structural a common alloy is cupronickel, the nickel does not
form a local moment below about 20 percent or so.
What's your specific application, and how low do you need the
moment to be?
The country of the coins will be central to getting a good answer. If
it's USA'n, then I'm sure there are FAQs out there which google could
scare up for him. Other large countries as well, I would think.
Nope------it's 10% copper, 90% silver, at least here in the US. It was the
standard for striking silver coins, likely the reason it's called *coin
silver*. Canada uses a lower silver content, I think 80%. Other
countries use varying percentages.
There is no nickel in coin silver, never has been, although nickels, during
the war years, were made from silver and manganese, with no nickel content.
It's easy to distinguish the war years nickels (aside from looking at the
dates) because the mint marks are very large. Likely none left in
circulation now, though. They were probably all taken out of circulation
when the silver content exceeded their face value, in the same manner the
rest of our silver coinage experienced.
The term "coin silver" has a specific meaning when used in the electrical
contact industry - and that is quite different than the term when used
in numismatic terms.
I seem to recall that somebody on RCM a long time ago researched this,
and found there was an appreciable amount of Ni in electrical contacts
that were called 'coin silver' and the term had its roots in germany
from long ago.
I suspect the original poster was not refering to silver gotten from
coins for his apparatus. The term seems to be a bit vague, but the
90/10 cu/ag number you cite seems pretty much the standard. If
that meets his needs, it will of course be non-magnetic - but there
may be other more mechanically desirable materials out there.
I still seem to remember somebody here posted historic details
on that alloy that included Ni though.
Are you shure that you don't confuse this with "new silveer" (Neusilber)
that has no silver at all. It is als called Alpaka:
and is used for contacts.
just guessing. If I'm off, ignore me.
Hardness Rockwell 15T, annealed 70, cold worked 83
Electrical conductivity %IACS 85
Ultimate tensile strength (psi), annealed 40000, cold worked, 75000
Elongation % in 2in , annealed 32, cold worked, 4
As to machinability, they do not list it, so this info is anecdotal
based on my own limited experience.
Fine silver maccines about like copper.
Sterling silver machines about like 260 brass
Coin silver machines slightly better.
Paul K. Dickman
But probably horrible in the way of contact value, however. Aluminum
enjoys forming aluminum oxide rapidly---which is not known for its good
Heavy duty silver contacts are made from tungsten powder and
silver------which yield the best of all worlds. Don't have a clue how
they'd machine, but I can't help but believe they'd be tough on tools.
I can well imagine, having machined tungsten on more than one occasion.
It's not for the feint of heart.
Refining the tungsten contacts was interesting. A prolonged boil in nitric
acid and water to remove the silver was required. Interestingly, some of
the contacts maintained their form, while others disintegrated. You could
tell when the silver had been totally removed by breaking a contact. Those
that broke easily were free of silver, while the others would have a
distinct line in the center, where silver was still present.
Umm, Harold, that wasn't one of the properties he listed.
They also use to be made from sintered silver, Wo, and Cd. I
knew a group at GTE labs that were trying to eliminate the Cd
Just thought the information might be useful. I can see it all now. An
aluminum oxide grinding wheel used as a contact. Somehow, it sort of
loses something along the way. On the positive side, it doesn't arc
I encountered the cad filled ones occasionally. It blended so well with the
silver that you weren't aware of its presence, yet there was a loss in
weight when the overall mass was processed. Had to be Cd. I can't help
but think that they were in better quality house switches and other light
duty devices. It's been too long to remember.
These were contacts for circuit breakers for GTE's product line.
Back in the early 80s there was a realization that putting a lot
of cadmium in products like that was a bad idea, even if it made
the breakers (contacts) work really well.
When breakers close they don't dry switch, there's a period when
they have to arc a bit to make good contact for passing high
current. My understanding is that somehow the Cd would flash on
opening, and make it easier to close for the next cycle.
They were trying to replace them with the above-mentioned Ag/Wo
sintered contacts I think. The shop was very good at pressing
and sintering stuff.
The guy doing the research ironically lived in Woburn, Mass, which
was the town that had its wells all contaminated by WR Grace, et al.
He used to bring his drinking water home from the lab in a gallon
jug every night. I thought it was ironic anyway, here was a guy
working to eliminate a toxic metal from a product, but at the same
time he had to deal with corporate irresponsibility in a very