On Tue, 05 Nov 2013 12:26:16 -0600, Tim Wescott
wrote:

I was going to say "acrylic", but then I realized that maybe I would be
narrowing it down too much.

How hard is it to machine a part out of hard clear plastic and then make
it clear again? Any gotchas? What plastic should one start with? What
question am I failing to ask?

The part will be cylindrically symmetric (i.e., turned on a lathe), about
1.5" diameter, 0.5" tall, and accuracy can be as sloppy as 0.01 in all
directions. But it would need to be "pretty".

Some plastic that is a bit more rugged in impact than acrylic would be
nice (do they make crystal clear Delrin?) but I can't think of anything
like that which would actually work in this case.
just sand it with progressively finer finishing paper and polish.
Made a couple yoyos with the young french exchange student we had with
us 15 or so years ago out of clear acrylic and they are just like
glass