To find the required RPM, look up the material, operation, and tool type in the table under "RPM for 20mm diameter" and scale RPM inversely with diameter. For example, if the work piece is only 10mm diameter, RPM needs to be doubled; if it is 40mm diameter, RPM needs to be halved.
Alternatively, use the "Cutting speed" table with the following formula: rpm = 1000 * cuttingspeed / (pi * diameter)
| Cutting speed (m/min) | RPM for 20mm diameter | |||||
|---|---|---|---|---|---|---|
| Turning | Drilling | Turning | Drilling | |||
| HSS | Carbide | HSS | HSS | Carbide | HSS | |
| Unhardened stainless steel | 20-35 | 70-120 | 15-25 | 320-560 | 1100-1900 | 240-400 |
| Mild steel | 20-35 | 90-135 | 20-30 | 320-560 | 1400-2150 | 320-480 |
| Copper & phosphor bronze | 30-35 | 60-65 | 20 | 480-560 | 960-1000 | 320 |
| Class 20 cast iron | 35 | 135 | 30 | 560 | 2150 | 480 |
| Other brass & bronze | 60-75 | 150-165 | 35-40 | 960-1200 | 2400-2600 | 560-640 |
| Wood & plastic | 60-150 | 150-450 | 20-90 | 960-2400 | 2400-7200 | 320-1400 |
| Free-machining brass | 90-105 | 180-200 | 50-55 | 1400-1650 | 2900-3200 | 800-875 |
| Aluminium | 150-180 | 335-365 | 30-120 | 2400-2900 | 5300-5800 | 480-1900 |
Source: Chegg.com