Tony Wells link=topic=1431.msg8295#msg8295 date=1301585410 said:
I have a box full of triangle insert tooling gathering dust. I use almost exclusively 80 deg diamond inserts. The only triangular inserts I use are threading inserts.
I was the same way until recently. I have quite an array of the triangular lay-down threading inserts, anvils and holders that get their share of use.
Recently I snagged a brandy-new Valenite VNCD-7462 solid carbide boring bar which takes TPG/TPGN 22x size inserts. It cost me just $55 for a bar that once sold for well over $200, a deal I couldn't pass up. Inserts are cheap and plentiful, so I found some Mitsubishi TPMR 221 inserts that have a molded-in chipbreaker form. The one major issue I have with using flat-topped TPG inserts in lathe work is that of having to rely upon the ill-conceived concept of using mechanical chipbreakers for chip control. The TPMR's help solve that problem. I've also picked up a pack of (free) TPG322 inserts which are of a whisker-reinforced ceramic grade for high-temp alloys and other very difficult-to-machine materials, so I bought a 1" shank turning holder should I ever need to use the inserts.