Insert, TPMT-222 Carbide

The 0.25" inscribed circle is a perfect fit for my smaller boring bars, and the chip breaker on these inserts really helps control those long stringy chips. I've been running them on 4140 steel and the edge holds up noticeably better than the cheaper inserts I tried before.

These insert the part of my lathe tool holder perfectly, and that 1/4" inscribed circle gives nice, rigid cuts on my small steel stock. The single-sided chip breaker clears the chips away cleanly, so I didn't have to stop and clear a bird's nest once.

The 11-degree relief on these TPMT-222 inserts gave me a noticeably cleaner finish on my stainless steel parts. They hold an edge well through a full run, and the single-sided chip breaker kept the swarf manageable.