Cathy,
I'd like to know what size round wire is used to make twisted wire bangles similar to the trademark David Yurman bracelet. I assume the wire would need to be straightened, annealed, pickled and polished before twisting. I'm also wondering what length of wires to start with, as the twisting will draw them up a bit.
I’m not sure how well the method would translate to the hollow tubes
that have been mentioned in this thread, but I twist wires together
from time to time in my work, and I find that it’s important to avoid
twisting the individual wires around their own axes while they’re
wrapping around their common axis, to prevent torsional stresses
within them. I use a variation on the “drop spindle” method.
First, you have to have something that will hold all of them in
close proximity, which, in my case, means three small holes in one
end of a fixture, very close together, connected to three holes at
the other end, spread apart. With the wires suspended from a common
point, passing down through that (starting at the holes that are
close together), and then attached to weights by means of swivels,
and separated by something to keep them from tangling, you can turn
the fixture to impart a twist, starting as close to the top as you
can get and moving down as the twist closes up.
It’s a lot easier for short sections than it is for long ones,
because you have to find somewhere to keep the extra wire if your
vertical space isn’t adequate for your wire length. 
Loren