Jon Anderson wrote in
rec.crafts.metalworking on Tue, 15 Feb 2011 11:15:14 -0800:

And am I pushing things skimming so little material off, should I step
up to 7/8 so as to remove more material from each side, or will this
just make it worse?

I usually turn Delrin, so this may not apply to flat stock, but I have
found that is seems to have a tight 'skin' on it. About .050" or so
thick. I think it's from the extrusion process. I would want to take
that much of each side. But if your stock was cut from larger stock,
that may not be the case.
--

Dan H.
northshore MA.