Insert, TCMT-1.81.51 Carbide

The 60° triangle shape fits my holder perfectly, and the single-sided chip breaker keeps the swarf from tangling around the tool. Machined a dozen parts in aluminum and the edge still looks clean.

Finally, a TCMT insert that actually seats flush in my holder without rocking—the 7° relief and single countersink make all the difference. Chip breaker works cleanly on aluminum at light feeds, and the 0.21875" IC is exactly as marked.

Mounted one in a TCMT holder and the 60° triangle cut a nice, sharp 90° shoulder on some 12L14 steel. The chip breaker worked just as advertised, clearing chips cleanly without any hassle.