I would reduce the SFM to about 120 and the feed to match. Try a DCMT with a 1/64 nose radius. The DCGT is an aluminum cutting insert, much too sharp of an edge for hard materials. DOC should be about the nose radius. I have found the Shars Tools inserts to be a pretty good value. A good compromise between the expensive name brand inserts and production. I use them in 304 SS and get an acceptable number of parts/insert.