Calculate milling RPM, feed rate, chip load per tooth, cutting speed and material removal rate for end mills and milling cutters.
| Material | HSS | Carbide | Indexable |
|---|---|---|---|
| Mild steel | 20 m/min | 120 | 150 |
| Carbon steel | 15 | 90 | 120 |
| Stainless steel | 10 | 60 | 80 |
| Tool steel | 10 | 55 | 70 |
| Cast iron | 18 | 100 | 130 |
| Aluminum | 80 | 250 | 350 |
| Brass | 70 | 220 | 300 |
| Bronze | 25 | 100 | 130 |
| Copper | 50 | 180 | 250 |
| Titanium alloy | 8 | 45 | 60 |
| Nickel alloy | 6 | 35 | 50 |
| Magnesium alloy | 100 | 300 | 400 |
| Engineering plastic | 100 | 300 | 400 |
| Cutter diameter | Light | General | Heavy |
|---|---|---|---|
| 2–3 mm | 0.01 mm | 0.015 | 0.025 |
| 3–4 mm | 0.015 | 0.025 | 0.040 |
| 4–6 mm | 0.020 | 0.035 | 0.055 |
| 6–8 mm | 0.030 | 0.050 | 0.080 |
| 8–10 mm | 0.040 | 0.065 | 0.100 |
| 10–12 mm | 0.050 | 0.080 | 0.120 |
| 12–16 mm | 0.065 | 0.100 | 0.150 |
| 16–20 mm | 0.080 | 0.125 | 0.180 |
| 20–25 mm | 0.100 | 0.150 | 0.220 |
Chip-load values are generalized starting points. Actual chip load should be selected from cutter manufacturer data and adjusted for engagement, machine rigidity and workpiece material.
How do I calculate milling RPM? RPM = 1000 × cutting speed ÷ (π × cutter diameter in mm).
How do I calculate milling feed rate? Multiply RPM by the number of cutter teeth and chip load per tooth.
What is chip load? Chip load is the approximate amount of material advanced per cutter tooth during engagement, normally expressed as mm/tooth or inches/tooth.
Does a 4-flute cutter feed faster than a 2-flute cutter? At identical RPM and chip load, yes. Doubling tooth count doubles the theoretical feed rate.
Should aluminum use higher RPM than steel? Often yes, because aluminum can generally tolerate substantially higher cutting speeds than many steels, but the exact value depends on alloy and cutter.
Can I use this calculator for CNC milling? Yes, as a starting-point calculation. Verify the final parameters against the cutter manufacturer's data and your machine's capabilities.
Why does radial engagement matter? A small radial engagement can permit different cutting conditions from a full-width slot. Tool engagement changes heat generation, chip thickness and cutting forces.
Why can the calculated RPM be too high for my machine? The mathematical RPM only follows the selected cutting speed and cutter diameter. Your spindle's maximum RPM may be lower, so use the highest suitable machine speed within the tool manufacturer's recommendations.
Are these cutting speeds exact? No. They are generalized starting references. Exact values depend on material grade, cutter geometry, coating, machine, coolant and engagement.