Insert, TPMB-321 Carbide

The single countersink on these 60° triangles sits perfectly flush in my tool holder. The 11° relief gives a clean, chatter-free finish on aluminum and mild steel.

Needed a new set for my lathe and these 60° triangles with the 11° relief cut through stock clean as can be. The single countersink hole made setup a breeze too.

Got these to replace some worn out inserts on a small boring bar, and the 60° triangle with no chip breaker works great for finishing passes. The 3/8" inscribed circle seats perfectly in my holder with no play. Cut aluminum and mild steel so far with nice surface finishes.