Composition of alloys

[Daniel Beardsmore]

Depending on model, Cherry M8 switch contacts used one of the following alloys for the upper block of each contact prism:

AuAg 26 Ni 3
AgPd 30
AuAg 10

I can't find anywhere that explains what these mean. Not the elements (those, I recognise), just the composition notation. (For example, why is "AuAg" distinct from "Ni" — it's like some kind of alloy nesting.)

[Blaise170]

If I understand what you are asking, I believe it's not really any different than standard elemental compounds. The first would be the equivalent of Au₁Ag₂₆Ni₃.

[Daniel Beardsmore]

Only 1 part gold in 30? I did wonder, but my guessing is not good enough: someone must know for certain.

So that would make M84x (the last) more gold. The first two (M81x and M82x) have prism contacts, while the last one has cylindrical crossbar, the same as MX switches. Some years ago (mid 2000s, I forget), MX returned to prism contacts.

[Blaise170]

It wouldn't actually surprise me, I imagine that the contacts are simply gold plated and that the majority of the contact is made of silver since it's a bit cheaper than gold but still highly conductive and then nickel for strength. On the flipside, gold has better corrosion resistance than silver which would also explain the coating.

[Daniel Beardsmore]

Contact material and structure is not well known. Gold plating was more common, but some types used gold inlay. (Examples found to date are listed under [wiki]metal contact switch[/wiki]; like all the similar pages, it still needs a lot of detail adding.)

Cherry however used a horizontally split prism, with the bearing surface being a solid alloy block. You can see this in the old catalogues.

What Cherry don't seem to show is the structure of the cylindrical contacts in M84 and MX switches.

There's a 400+ page book on nothing but electrical contacts — I guess if anyone here would read such a thing, it would only be me …