Insert, CCMT-32.51 Carbide

The 80° diamond profile gives me a nice clean corner on finishing passes, and the 7° relief keeps it from rubbing in the bore. Chip control with the single-sided breaker has been solid on 1018 steel too.

Bought a ten pack for boring small holes on the lathe and the 40°-60° countersink seats the screw dead flat every time. The single-sided chip breaker curls the stringers off clean, no birdnesting like my old inserts. 3/8" IC is small enough to reach into tight bores without rubbing.

The 80° diamond geometry with the 7° relief clears the shoulder on my facing cuts without rubbing. Chip control on 1018 steel has been clean, no birdnesting at all. The 3/8" IC fits my holders exactly as expected.