Burnished finish

adamlaneus

They are burnishing the die, correct?

They don't burnish the master die, but the one made from it I suppose? Or is it more complex than this?

I mean, burnishing the coin seems no different than whizzing. And it is impractical to do to every coin.

SpaceMonkey

the burnishing process is done to the planchet blanks BEFORE striking. tumbled with pellets and such.







-sm

adamlaneus

Okay. Good answer. Now it begs another question.

The background:
One thing that burnishing does is hardens the surface. This is one reason why I had mistakenly supposed that you burnish a die.
I would have thought that the process of stamping a coin under extremely high pressure is going to pretty much eliminate the original surface and leave you with the die impression.
But the crystals near the surface of the metal are important. Burnishing changes them. This may make the die strike rather different.

The question.
Is burnishing then done for surface hardness characteristics? Or the finish characteristics? Some of both?
This is something I thought I knew. But with a little curiosity, I find I know very little.

The other question.
What are good examples of series that have otherwise identical production but with burnished/non burnished finishes?

SpaceMonkey

i do believe the burnishing process is for the finish only... the hardening is done during the annealing process (passing through a furnace)

ASE UNCS would be the best example i could think of for the Burnished/UnBurnished versions.





-sm

Rupert305

Glossary definition:

burnishing: a process in which the surfaces of a planchet or coin are made to shine through rubbing or polishing