Well, it seems to me generally this idea persists because it works.
At least it works sufficiently well for many purposes. I do not know
if it is a few microns or a few tens or fifties of microns or more,
but tumbling work hardens small pieces made from thin sheet (18-24
g). So perhaps the uniform surface hardening covering the pieces is
enough to stiffen it. I do it routinely.
Of course I use it for decorative elements, not things like clasps
and ear wires.
I do not know if it is a few microns or a few tens or fifties of
microns or more, but tumbling work hardens small pieces made from
thin sheet (18-24 g). So perhaps the uniform surface hardening
covering the pieces is enough to stiffen it
Personally I tend to agree, although I respect what James Binnion and
others say on the subject. I see it a little like wearing a coat of
armour. I know I’d be walking around a lot more stiffly if I had a
metal suit on, so an even coating of slightly harder metal must
surely give the overall piece some degree of extra hardness, no?
Whether or not it’s enough is debatable, depending on the level of
wear a piece is expected to have.
Well, it seems to me generally this idea persists because it
works. At least it works sufficiently well for many purposes.
It provides an impression of increased hardness because it has
produced a strain in the skin of the metal but like an egg shell the
impression of hardness is illusory if you put any real stress on it.
It is so thin that if you polish after tumbling you will remove the
hardened layer. So I would dispute that it makes any real difference
in the longevity of the item which after all is the main reason for
wanting a harder item.
Include some tin in the copper, and make a bronze, is the only way
I can think to harden up your copper. You shouldn't need a lot of
tin, just a smidge (a technical term, closely related to the term
"bugger all").
I just have to say one thing. Thanks. You made my day with that last
sentence and literally had me LOL.