Anthony wrote in
:

snip

Agreed Dan, however, within the budget of just about anyone, PCD would
be the next choice. Monocrystal diamond tools in any useful size are
*extremely* expensive. We do use some, but only in applications where
the specific advantages they offer are absolutely required.

PCD grain size (PCD Grade) will determine, to a large degree, the
surface finish you get. Using a fine grade (say GE 1500), will provide
a better finish, but really should only be used for light finishing
cuts, as you have much smaller diamond crystals which are easier to
rip out of the binder along the edge. However, you do get a much
smoother edge on the tool, with smaller binder gaps between crystals,
hence better surface finish. You want to use a very coarse grained PCD
tool for roughing operations. The crystals are larger, but the binder
has a better grasp on the crystals, so they aren't as easy to rip out.
You will have a rougher surface due to the larger gaps of binder
between crystals, however.

Unless you are doing mirrors, or some automotive/electronics/NASA type
stuff, the differences are unnoticable to the average machinist. You
can really only see the differences when doing microscopic inspections
of the surface.

Anthony,
I got a quick question for you. I read an article in IDR (Industial
Diamond Review)a couple of years ago, where DeBeers did some test
cutting in Titanium using PCD tooling. The economics looked pretty good.
Have you had a chance to try them in Titanium? My Kennametal rep was
going to get an insert for me, it was the same tool used in the study,
but it wasn't available yet. I'd forgotten about it until now. I'd like
to hear from anyone cutting Ti with diamond tools.

Dan