Overview The TNMG 160404-PM 4215 is a double-sided negative triangular turning insert — 60° head angle, 0° clearance, 9.525 mm inscribed circle and 0.4 mm corner radius. Because both faces carry a chipbreaker, one insert gives six effective cutting edges, which is what makes the T-shape economical in production turning. PM is sandviks's medium chipbreaker geometry: a general-purpose steel geometry designed to control chips across a wide feed window rather than optimise a