CNC Turning for Alloy Steel 4140
4140 alloy steel turns predictably with good chip formation. In the annealed state, it is straightforward to machine. Pre-hardened material requires more attention to tooling and parameters.
Recommended Machining Parameters
| Parameter | Value |
|---|---|
| Achievable Tolerances | ±0.02 mm (±0.0008") |
| Surface Finish | Ra 0.4-1.6 μm |
| Cutting Speed | 150-250 m/min (annealed) |
| Feed Rate | 0.10-0.30 mm/rev |
| Tooling Recommendations | Carbide inserts grade P20-P30 with TiCN or TiAlN coating. Use heavy-duty insert grades for pre-hardened. |
Expert Machining Tips
1
Use inserts rated for interrupted cuts if pre-hardened
2
Flood coolant for heat dissipation
3
Chip-breaking inserts recommended
4
Reduce speed 30-40% for pre-hardened stock
Common Parts Made
Shafts and axles
Coupling hubs
Sprocket hubs
Piston rods
Toolholder bodies
Machining Challenges
- Pre-hardened condition wears tools faster
- Chip control at heavy depths of cut
- Work-hardened skin from hot rolling