once the posts are welded in place you tumble the earrings in steel
shot for a few days to harden up the posts and planish your
earrings. After this step if you are not happy with the finish you
the trouble with this is that although this will slightly harden the
surfaces of the posts, the work hardening only goes to a very shallow
depth, giving you a slightly hardened surface, but a post that is
almost as easy to bend as before.
Much more effective is to twist the wire. This stretches and bends
and distorts the metal through the whole thickness of the wire. In
and the process, if you hold the wire by it’s tip only, the wire
twists the most where the wire is softest, work hardening that area
the most. Thus you end up with a wire that’s pretty uniform in
hardness throughout it’s length, and the length and dimensions of the
wire don’t change when you do this. In some cases, you may find a
slight twist marking on the wire, if it had any striations from the
wire drawing process, and if this bothers you, THEN tumble, which
will mostly get rid of that mark.
There is a widely held (and oft repeated on this list) misconception
that steel shot tumbling offers a lot of work hardening. It doesn’t.
While there IS some hardening, it’s a thin surface effect only,
affecting resistance to wear perhaps, but not appreciably changing
the ease with which metal would bend or be prone to distortion,
stretching, etc, in use. Work hardening requires that the metal be
distorted enough past it’s elastic limit that the metal crystals are
permanently changed in shape, and the crystal boundaries stretched
and distorted. Usual steel shot tumbling simply does not exert enough
force on the metal to do that beyond that very thin surface layer.
There’s a similar misconception I sometimes see here where someone
(usually someone with some limitations in experience and training,
though not always) will claim that hitting the metal with a soft
(rawhide, etc) mallet will harden sheet metal. Again, no it doesn’t.
It may surprise the metal and spill it’s cup of coffee, but it
doesn’t sufficiently distort the crystal structure, even if it may
slightly serve to flatten a slightly warped shape. Do the same thing
with a metal planishing hammer though, which measurably thins the
metal as well as leaving nice attractive (sometimes)
hammer/planishing marks on the metal, and then you get fairly quick
work hardening, as the effect on the crystal structure is much the
same as you’d get with a rolling mill thinning the metal (though the
latter is more directional than planishing)
Hope that’s useful