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In article , "Ed Huntress" wrote:
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I haven't used them enough to give a real thorough evaluation, but the
positive rake inserts I got from Rouse Arno seem to work very nicely. The
inserts I have are razor sharp.

http://www.rouse-arno.com/products/prod_index.htm

I got a set of inserts & holders on sale at the Eastec machine tool show
2 years ago. I got a set with 3/8" square shanks, and liked them so much
I ordered the 1/2" square set before the show discount expired.

Doug White

Arno was promoting their positive-rake inserts back when I was active in the
field, so they probably have plenty of experience with them. The first time
I saw really sharp, thin-edged positive-rake carbide inserts was in the
mid-90s. They were made by some German company, and I was absolutely amazed
that those things could hold up in production cutting. But they do,
apparently, and there are a lot of new cutting tool products out there that
should answer problems we've had with hard tool materials on flexible old
machine tools.

The one I'd really like to see is tools made of Crucible CPM Rex 121. It's a
sort of extreme high-speed steel, sometimes called a "bridge" material
because it bridges the performance and application gap between HSS and
carbide. It ought to be the answer to lots of applications that need sharp,
tough, positive-rake cutters that are hard enough to cut hardened steel on a
small lathe. With that and a high-cobalt submicrograin carbide we could fill
in a lot of gaps.

Crucible only makes (or made) 121 in small quantities, and those go to
wear-part and press tooling. The last time I talked to them, which was maybe
four years ago, they planned to make it available for cutting tool
manufacturers once they got their production up. Maybe they already have.

It's a powder-metallurgy high-speed steel with extremely high percentages of
carbide-forming alloy, particularly vanadium.

This sounds pretty neat. I've been wondering why somebody doesn't make
HSS (or exotic steel alloy) inserts that could be used with carbide
tooling. It may just be that the fabrication costs don't match up with
the perceived market. Being able to pop a sharp insert into a holder
without having to take things apart & regrind your tool strikes me as a
big advantage.

Doug White