"DoN. Nichols" wrote in message
...
According to Harold and Susan Vordos :

"jremovespamblockroncallo roncallo @snet.net" "jremovespamblock
wrote
in message et...
Does anyone know how to machine polyurithane. I have to bore a tapered

[ ... ]

If you're trying to
use carbide insert tooling, I'm of the opinion you'll never achieve your
goal.

Well ... that depends. With *most* carbide insert tooling, I
totally agree. However, I do have some nicely sharp *uncoated* carbide
insert tooling in 55 degree diamond shape which fit the shanks for my
Compact-5/CNC. Any time you get a coated insert, you can bet that it is
not particularlys sharp, but some uncoated can be sharp enough. (I
often use these even on the much larger 12x24" Clausing when I want a
particularly sharp tool.)

These show signs of being ground to finish after being formed,
which probably accounts for the major part of the difference.

I use a diamond ground insert (RB), too, which would be sharp enough, but
sharp isn't enough for this material. If you haven't attempted to machine
it, it's hard to understand. It machines much like rubber. It requires
considerably more positive rake than is available from insert tooling, plus
a broad, deep chip breaker (if desired), thus my comment. I have no doubt
that a successful tool could be ground in carbide if one cared to spend the
time.

Harold