Charlie wrote:

The advantage to negative tooling is you can turn the insert over thus
you double the usable edges.

That is why I am using what are called negative-positive inserts,
TNMP-321s. What _looks_ like a chip breaker groove isn't. The grove
goes right to the edge giving the insert a ten degree positive rake. My
holders
http://www.metalwebnews.com/howto/toolholder/toolholder.html
have a five degree "droop" on the nose. This results in five degrees
clearance and five degrees positive rake. And six points for ~Cdn$5!

Ted