TNMG turning inserts are one of the core indexable inserts in CNC machining, widely used in steel, stainless steel, cast iron, alloy steel, and hard turning operations. Their iconic negative triangular geometry and six effective cutting edges deliver outstanding cost efficiency and stability.
This article provides a deep look into TNMG insert geometry, specifications, coating technologies, chipbreaker design, and tips on choosing the right TNMG model such as TNMG1604, TNMG331, TNMG332, and TNMG432.
1. TNMG Insert Geometry & Functional Advantages
TNMG inserts belong to the ISO code for triangle shape (T), 0° relief angle (N), tolerance (M), and chip groove (G).
Why TNMG geometry is preferred:
6 total cutting edges (3 per side) → lowest cost per edge
Negative rake → stronger cutting edge for heavy load
Symmetrical design → balanced performance and rigidity
Suitable for steel, cast iron, stainless & alloy steel
Excellent heat resistance under high-speed turning
2. TNMG Size Options: TNMG1604 / TNMG331 / TNMG332 / TNMG432
TNMG inserts have standardized sizes in global machining.
Table 1. TNMG Standard Sizes
| Model | Cutting Length | Thickness | Hole Size | Corner Radius | Remarks |
|---|---|---|---|---|---|
| TNMG1604 | 9.7 mm | 4.76 mm | 3.81 mm | 0.4–1.2 | Most popular |
| TNMG331 | 9.7 mm | 4.76 mm | 3.81 mm | 0.4 | Precision |
| TNMG332 | 9.7 mm | 4.76 mm | 3.81 mm | 0.8 | Medium machining |
| TNMG432 | 12.7 mm | 4.76 mm | 5.56 mm | 0.8 | Larger DOC |
Carbide TNMG Inserts
Best for: steel, stainless steel, cast iron
Coatings: TiAlN, AlTiN, CVD multilayer
Balanced toughness and wear resistance
Cermet TNMG Inserts
Best for: low-carbon steel finishing, stainless finishing
Smoothest surface finish
Ceramic TNMG Inserts
Ideal for high-speed machining of cast iron and superalloys
CBN TNMG Inserts
For hardened steel HRC 50–65
Extremely long life under dry cutting
4. Chipbreaker Types & Their Applications
Common Designs
MP / MS → medium machining
MA → finishing
MK → stainless steel
MR / R → roughing
HF / HR → heavy cutting
Chipbreaker geometry strongly affects chip flow and surface finish. Choose narrow geometry for finishing and deeper geometry for roughing.
5. TNMG Insert Holders You Should Know
Common TNMG holders:
MTGNR / MTGNL – 95° approach
PTGNR / PTGNL – high rigidity
STGNR / STGNL – general turning
6. TNMG Insert Price Advantages
China produces the most complete TNMG ranges with:
Competitive pricing
High-performance coatings
OEM/ODM customization
Stable supply for distributors
7. Quick Selection Guide
| Material | Grade | Chipbreaker | Recommended Model |
|---|---|---|---|
| Steel | P25–P35 | MP | TNMG332 |
| Stainless | M20–M30 | MK | TNMG331 |
| Cast Iron | K10–K20 | KR | TNMG432 |
| Hardened | CBN | — | TNMG1604 |