Machining data
4340 Steel speeds & feeds
Tough aerospace alloy steel — keep the edge cool and the chip load consistent. Below are RobbJack's tested starting parameters by diameter — then open the calculator to tune them to your exact tool, depth of cut, and spindle.
| Diameter | Recommended tool | Flutes | SFM | RPM | Feed (IPM) | Chip load (in) |
|---|---|---|---|---|---|---|
| 1/8" | XG-400-04 | 4 | 415 | 12,682 | 15.2 | 0.0003 |
| 3/16" | NS-401-06 | 4 | 415 | 8,455 | 16.9 | 0.0005 |
| 1/4" | SPS-401-08-010 | 4 | 415 | 6,341 | 17.8 | 0.0007 |
| 3/8" | SPS-401-12-010 | 4 | 415 | 4,227 | 23.7 | 0.0014 |
| 1/2" | SPS-401-16-010 | 4 | 415 | 3,171 | 25.4 | 0.0020 |
| 3/4" | SPS-401-24-010 | 4 | 415 | 2,114 | 20.3 | 0.0024 |
Starting parameters for roughing/profiling with a rigid setup — always verify on your machine, tool, and fixturing. Open the calculator to enter your exact depth of cut, spindle RPM/HP, and coating, and to get finishing values and a printable setup sheet.