I think the natural is the denser "machine grade" -- just never used
it but have used the
common haircell black abs.

I'm trying to find a plastic that will take paint well (and ABS does)
but also machines well.

The common ABS is ok but the edges end up pretty rough and even
sanding doesn't help much
(1/4" thick) -- perhaps I can get a better edge with the "machine
grade".

I'm also going to try to have some ABS cut with a waterjet and look at
that.