OverviewThe CNMM 644-PR 4425 — ISO designation CNMM 19 06 16-PR 4425 — is a heavy-duty turning insert for roughing steel on large, rigid machines. Its 19.05 mm inscribed circle and 6.35 mm thickness put it in a different class from the 12 mm inserts used for general turning: more carbide under the edge, more heat capacity, and far greater resistance to impact. The insert is single-sided: the chipbreaker is on one face only, giving two effective cutting edges. That is a