Selecting the right carbide insert is one of the highest-leverage decisions in CNC machining. The correct insert extends tool life, improves surface finish and reduces cost per part. Here is a practical framework used by our engineers.
1. Decode the insert naming system
Most carbide inserts follow the ISO 1832 standard. Take WNMG080404 as an example:
- W — insert shape (trigon with 80° included angle)
- N — clearance angle (0°)
- M — tolerance class
- G — chip breaker / hole type
- 08 — inscribed circle size in mm (8mm)
- 04 — thickness in mm (4mm)
- 04 — nose radius in mm (0.4mm)
Common shapes: WNMG (80° trigon, general turning), CNMG (80° rhombus, heavy turning), TNMG (60° triangle, light to medium turning), SNMG (square, 90° shoulder), DNMG (55° rhombus, profiling), CCMT (80° rhombus with hole, finishing).
2. Match the coating to the workpiece material
| Workpiece material | Recommended coating | Typical grade |
|---|---|---|
| Steel (carbon & alloy) | CVD TiC-Al2O3-TiN | P-grade (e.g. YB6425) |
| Stainless steel | PVD TiAlN | M-grade |
| Cast iron | CVD Al2O3 | K-grade |
| Aluminum alloys | Uncoated or diamond | N-grade |
| Hardened steel (HRC 45+) | CBN / PVD | H-grade |
3. Choose the nose radius
- 0.2mm — fine finishing, small corner features
- 0.4mm — general finishing, most common
- 0.8mm — roughing, higher feed rates
- 1.2mm+ — heavy roughing, maximum material removal
A larger nose radius gives a better surface finish but increases cutting forces. When in doubt, start with 0.4mm.
4. Common mistakes to avoid
- Using a finishing grade for roughing (rapid edge breakdown)
- Ignoring the chip breaker — a mismatched breaker causes poor chip control
- Over-speeding the spindle without checking the insert’s recommended cutting data
- Mixing grades across the same tool holder
5. Still unsure? Ask us
Send us your workpiece material, operation type and machine power. Our engineers will recommend the right grade, geometry and cutting parameters — usually within one working day.