Machining data
4140 Steel speeds & feeds
Common alloy steel — a 4-flute AlTiN-coated tool at moderate SFM is the reliable starting point. 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 | 400 | 12,224 | 14.7 | 0.0003 |
| 3/16" | NS-401-06 | 4 | 400 | 8,149 | 16.3 | 0.0005 |
| 1/4" | SPS-401-08-010 | 4 | 400 | 6,112 | 17.1 | 0.0007 |
| 3/8" | SPS-401-12-010 | 4 | 400 | 4,075 | 22.8 | 0.0014 |
| 1/2" | SPS-401-16-010 | 4 | 400 | 3,056 | 24.4 | 0.0020 |
| 3/4" | SPS-401-24-010 | 4 | 400 | 2,037 | 19.6 | 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.