"Lloyd E. Sponenburgh" wrote in message
...

"Harold and Susan Vordos" wrote in message
...

"jim rozen" wrote in message
...
In article , Robert Latest says...

Mechanical as regards strength, hardness, and machineability.

Use aluminum, it will be better than Cu/Ag 90/10 alloy in all
of those catagories.

Jim


But probably horrible in the way of contact value, however. Aluminum
enjoys forming aluminum oxide rapidly---which is not known for its good
electrical properties.

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.

They're right tough on contact burnishers!

LLoyd

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.

Harold