CNC Machining Speeds and Feeds Calculator
Calculate optimal RPM and Feed Rate for milling and turning. Includes a material library (Aluminum, Steel, Titanium) with auto-filled SFM and Chip Load data.
About
Running a CNC machine at incorrect speeds results in poor surface finish, shattered end mills, or work-hardened materials. This calculator determines the optimal Spindle Speed (RPM) and Feed Rate based on your specific material and tool diameter. It eliminates the guesswork by referencing a built-in library of surface footage (SFM) and chip loads for common metals and plastics, helping machinists maximize material removal rates (MRR) without sacrificing tool life.
Formulas
The Spindle Speed depends on the Surface Feet per Minute (SFM) and the tool diameter.
The Feed Rate depends on the RPM, number of flutes (teeth), and Chip Load per tooth.
Reference Data
| Material | Hardness (HB) | SFM (Carbide) | SFM (HSS) | Chip Load (1/2" Endmill) |
|---|---|---|---|---|
| Aluminum 6061 | 95 | 600 - 1200 | 250 - 350 | 0.004 - 0.008" |
| Steel 1018 | 126 | 350 - 550 | 80 - 100 | 0.002 - 0.004" |
| Stainless 304 | 201 | 150 - 250 | 40 - 60 | 0.001 - 0.003" |
| Titanium 6Al-4V | 334 | 120 - 180 | 30 - 40 | 0.001 - 0.002" |
| Brass C360 | - | 400 - 800 | 150 - 250 | 0.003 - 0.006" |
| Delrin (Acetal) | - | 500 - 1000 | 300 - 500 | 0.005 - 0.010" |
| Tool Steel D2 | 255 | 100 - 180 | 30 - 50 | 0.001 - 0.002" |
| Cast Iron (Gray) | 180-300 | 250 - 450 | 60 - 80 | 0.003 - 0.005" |