On Wed, 23 Mar 2005 07:58:34 -0800, Grant Erwin
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It uses the following inserts:
TPG/TPU/TPC-321,2
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According to the catalog the ANSI nomenclature is:

T = Triangle

P = 11 degrees relief

G = ground with +/- 0.001 inch tol on the I.C. [outside]
dimensions and +/- 0.005 on the thickness.

U = unground with +/- 0.010 on the I.C. and +/- 0.005 on the
thickness

C = ground with +/- 0.001 on the I.C. and +/- 0.001 on the
thickness.

I have used both TPU and TPG and could not tell any difference.

Last digit in 320,321,322,323 is the nose radius.
0 = 0.004 inch nose radius
1 = 1/64 inch nose radius
2 = 1/32 nose radius
3 = 3/64 nose radius
4 = 1/16 nose radius

I find that the nose radius does make a difference. The bigger
nose radius tends to give better finish and longer insert life,
but some materials require smaller nose radius to avoid chatter
and squeal.

Coated inserts seem to give better finishes for me and lost
longer. TiN [gold] is good I have not yet tried the TiC
coatings. The Al2O3 coating dosen't work well on aluminium but
is great for cast iron.

For home shop and light volume production coated inserts appear
to eliminate the need for C2 and C6 grades, and has allowed us to
use C6 for everything.

A google search for tpu-322, etc. turns up lots of bargins.

GmcD