Pramet TNMG Insert. TNMG Negative Turning Insert for use with DTGN, DTFN, PTFN, PTGN, PTTN, PTFN and MTJN Holders and Bars. T9315. Excellent for machining Steel Acceptable for Cast Iron and Hardened Steels. T9325. Excellent for machining Steel and Stainless Steel Acceptable for Cast Iron. T9335. Excellent for machining Steel Acceptable for Stainless Steel