Tim Wescott wrote:
Think prop spinner for a model airplane (is this sounding familiar?)

Assuming that I'm not turning from solid (oh, it sure is!), how hard
is this going to be on a Smithy-sized lathe (7" swing over the ways,
cheap Chinese construction). I'm thinking that I'd use soft aluminum,
no thicker than 50 mil and probably more like 30 or 40.

I've never spun metal before, but I've seen videos so I know I'll be
able to do it with hand-made tools, like a pro, the very first time.

While we're on the subject -- how do you spin a piece that's rounded
on the end? Make a dimple in your sheet, then spin down from there?
You've got to have some surface area on the tail stock, don't you?

How big is the part?. What you're proposing is quite doable and if
you're willing to have a go can be learned without too much trouble.
When I taught myself to spin, about 1997, there was not that much
information on the internet but quite a bit more now. I started with a
prop spinner shaped part, I wouldn't now as there are much easier forms
to start with, but I persevered after destroying my initial couple of
blanks and managed to get a complete part by number 6. The main thing
with a part with a small initial clamping area is to get the metal laid
down properly to support the blank or it'll fatigue and break near the
clamping piece. The laying down of the material onto the spinning chuck
is done on the pass back towards the tailstock. A couple of pieces I've
done of this nature are here
http://www.metal-arts.co.uk/temp/Spinning/spin1.jpg and
http://www.metal-arts.co.uk/temp/Spinning/spin2.jpg . The aluminium one
is easy as that was 1050 and doesn't really seem to work harden, the
brass one was probably 10% spinning and 90% annealing between spinning.