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Description
CNMA 120412 turning insert – 80° indexable rhombus
| Technical data | |
|---|---|
| Side length l | 12.9 mm |
| Insert thickness s | 4.76 mm |
| Hole diameter d1 | 5.16 mm |
| Corner radius rε | 1.2 mm |
| Inscribed circle diameter IC | 12.7 mm |
| ANSI code | CNMA 433 |
NTH2 rhombic carbide insert – applications and design
double-sided 80° rhombus with a hole, without a chip breaker
The CNMA 120412 turning insert is a double-sided, rhombic indexable insert made from grade NTH2 cemented carbide, intended for turning cast iron and alloy and austenitic steels. Shape C, a rhombus with a 80° corner angle, combines two usable corners per side with high cutting edge rigidity. The negative geometry with a 0° clearance angle allows both faces of the insert to be used — a total of four cutting edges. The type A design has a mounting hole and a smooth rake face without a chip breaker, making it suitable for the short chips produced by brittle materials. The nose radius rε of 1.2 mm strengthens the tip and favors roughing at higher feed rates.
Key advantages of the NTH2 cemented carbide insert
- Four cutting edges — 2 usable 80° corners on each of the two sides reduce the cost per cutting edge compared with single-sided inserts.
- Grade NTH2 for ISO groups K and M — carbide for malleable and gray cast iron (K10-K25) and alloy and austenitic steel (M10-M25).
- Corner radius rε 1.2 mm — a strong, durable corner for roughing at higher feed rates and greater depths of cut.
- The 80° corner angle provides a rigid cutting edge that withstands interrupted cuts and hard casting skin.
- Dimensions according to ISO 1832: IC 12.7 mm (1/2″), side length 12.9 mm, thickness 4.76 mm — compatible with holders with size 12 rhombic C pockets.
- The type A design with a mounting hole and a smooth rake face is suited to the short, easily evacuated chips produced by cast iron.
Applications and cutting data selection for the diamond-shaped insert
The CNMA 120412 insert (also written without a space as cnma120412) is suitable for turning housings, bushings, pulleys, and flanges made of gray and malleable cast iron, as well as alloy steel components. Grade NTH2 covers ISO groups K10-K25 for cast iron and M10-M25 for austenitic steel, allowing a single insert to handle semi-finishing and roughing. The large nose radius of 1.2 mm distributes the load over a longer section of the edge, reducing chipping during interrupted cutting and machining through hard casting skin. This cemented carbide indexable insert is offered as a replacement for TNMG inserts in similar applications.
Calculate spindle speed using n = 1000·Vc/(π·D): for a shaft with a diameter of 80 mm at an approximate cutting speed of Vc = 120 m/min, the result is approximately 477 rpm. Select the speed and feed rate to suit the casting hardness and machining allowance, maintaining a constant feed rate for even corner loading. For gray cast iron, the cutting insert is most often used without coolant, while for alloy steels, cooling and a lower speed are advisable. Inserts of this type are supplied by the Polish manufacturer Baildonit, known for cemented carbide turning tools.
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Application limitation
Type A is an insert with a hole but without a chip breaker — the smooth rake face works well with the short chips produced by cast iron. For ductile carbon steels that produce long chips, choose an insert version with a chip breaker.
Rhombic insert designation decoder according to ISO 1832
how to read the CNMA 120412 code — designation positions 1–7
Designation CNMA 120412 according to the standard ISO 1832: 4 letters describe geometry and construction, 3 numeric codes describe dimensions. Each field has a number, an icon, and a brief description.
Frequently asked questions about the CNMA 120412 insert
design, material selection, and turning parameters
Four — the 80° diamond has 2 usable corners per side, and the negative geometry (clearance angle 0°) allows both sides of the insert to be used. When a corner becomes dull, simply index the insert in the pocket without changing the holder.
Grade NTH2 covers groups ISO K10-K25 (gray and malleable cast iron) and M10-M25 (alloy and austenitic steel). It is suitable for semi-finishing and roughing, including interrupted cuts and machining through hard casting skin.
Only in corner radius: 1.2 mm is a roughing version for higher feed rates, 0.8 mm is a general-purpose version, while 0.4 mm is used for finishing. The other dimensions (IC 12.7 mm, thickness 4.76 mm) are identical.
The letter A in the code denotes an insert with a mounting hole and a smooth rake face, without a formed chip-breaking groove. Chip control then depends on the cutting parameters; the design is suited to the short chips produced by cast iron and is less effective with the long chips produced by ductile steels.
Product accessories
Carbide insert CNMA 120408 UC5115 Mitsubishi
Reference: 12341 In stock > 10 items
€3.95
€4.86 brutto
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| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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