Match the workpiece metal, cutting tool and machining operation to a practical starting cutting speed, then calculate spindle RPM.
| Material | HSS | Cobalt | Carbide | Cermet | Ceramic |
|---|---|---|---|---|---|
| Mild steel | 25 | 35 | 150 | 180 | 300 |
| Carbon steel | 20 | 30 | 120 | 150 | 250 |
| Alloy steel | 15 | 25 | 100 | 130 | 220 |
| Stainless steel | 12 | 18 | 80 | 100 | 180 |
| Tool steel | 12 | 18 | 70 | 90 | 160 |
| Cast iron | 20 | 25 | 120 | 150 | 250 |
| Aluminum | 80 | 120 | 300 | 350 | 500 |
| Brass | 70 | 100 | 250 | 300 | 450 |
| Bronze | 30 | 40 | 120 | 150 | 250 |
| Copper | 50 | 65 | 200 | 250 | 350 |
| Titanium alloy | 8 | 15 | 50 | 60 | 100 |
| Nickel alloy | 6 | 12 | 40 | 50 | 80 |
| Magnesium alloy | 100 | 140 | 350 | 400 | 600 |
| Engineering plastic | 100 | 150 | 300 | 350 | 450 |
Reference values are generalized starting points in m/min, not universal manufacturer specifications.
What is metal cutting speed? It is the surface speed between the cutting tool and workpiece, normally expressed in m/min or SFM.
How is RPM calculated? RPM = 1000 × cutting speed ÷ (π × diameter in mm).
Why does tool material matter? HSS, carbide, ceramic and other tool materials have different thermal and wear characteristics, allowing different cutting-speed ranges.
Why can carbide run faster than HSS? Carbide generally maintains useful hardness at higher temperatures, allowing higher cutting speeds when the machine and tooling are suitable.
Should drilling use the same speed as turning? Not necessarily. Drilling has different chip evacuation and heat conditions and may require a more conservative starting speed.
Does diameter affect RPM? Yes. At a constant cutting speed, larger diameters require lower RPM.
Can this calculator be used for CNC machining? Yes, as a starting calculation. Final parameters should be checked against the exact tool manufacturer's data and machine limitations.
Are these cutting speeds exact? No. Material grade, hardness, heat treatment, tool coating, geometry, coolant, engagement and machine rigidity all affect the appropriate speed.