On Fri, 18 Dec 2009 22:39:53 -0500, GeoLane at PTD dot NET wrote:

I'm looking at R8 carbide indexable end mills from CDCO to use for
cleaning up rusty stock and squaring up stock. One says it uses tpg-32
inserts. Are those the same as tpg-322?

Another alternative is a similar 2.5" indexable end mill, which uses a
different insert. SPG422 carbide Positive rake, 15 Degree lead angle I
have a Bridgeport with the 2J head. Which of the two is more likely to
give a good finish on hot and cold rolled steel?

What difference does the positive rake and 15º lead angle make?

RWL

I am just adding to what the previous posters have said. The advice they
have given is sound. I would only like to add the pros and cons to the
two styles you are looking at. I am probably missing some, but:

Triangle inserts:
pro: can face mill up to a square corner.
con: slightly weaker and more prone to breakage. Lighter cuts will need
to be taken. only 3 edges per insert.

squa
pro: stronger, more heavy cuts can be taken.
con: can't mill up to a shoulder(when used with the lead angle shown)

Of the particular holders shown, some things to consider:

a four insert tool will be faster that a 3 insert tool. Probably not a
big deal for a hobbyist.

The square insert tool lead angle will slightly improve insert life and
can be helpful on brittle materials to prevent edge breakage (of the
workpiece). It also looks to have more axial rake than the triangle
holder. This will improve surface finish, and is slightly easier on the
machine. The triangle inserts seem to begin the chip with a maximum edge
force, and the result is a noticable difference in the noise, in my
experiences with the two types. It's probably harder on the machine.

Of the two, I personally would probably use the square insert holder 90
percent of the time.