Calculate a practical starting RPM and feed rate for drilling metal from drill diameter, workpiece material, drill type and feed settings.
| Material | HSS | Cobalt | Carbide |
|---|---|---|---|
| Mild steel | 25 m/min | 35 m/min | 80 m/min |
| Carbon steel | 20 | 30 | 70 |
| Stainless steel | 12 | 18 | 45 |
| Tool steel | 12 | 18 | 40 |
| Cast iron | 20 | 25 | 60 |
| Aluminum | 60 | 80 | 150 |
| Brass | 80 | 100 | 180 |
| Bronze | 30 | 40 | 90 |
| Copper | 50 | 65 | 120 |
| Titanium alloy | 10 | 15 | 35 |
| Nickel alloy | 8 | 12 | 30 |
| Magnesium alloy | 80 | 100 | 180 |
| Drill diameter | Light | General | Heavy |
|---|---|---|---|
| 1–2 mm | 0.012 | 0.015 | 0.020 |
| 2–3 mm | 0.015 | 0.025 | 0.035 |
| 3–5 mm | 0.025 | 0.050 | 0.070 |
| 5–8 mm | 0.050 | 0.100 | 0.140 |
| 8–12 mm | 0.080 | 0.150 | 0.220 |
| 12–16 mm | 0.120 | 0.200 | 0.300 |
| 16–20 mm | 0.160 | 0.250 | 0.380 |
| 20–25 mm | 0.200 | 0.300 | 0.450 |
| 25–30 mm | 0.250 | 0.400 | 0.550 |
How do I calculate drill RPM? Use RPM = 1000 × cutting speed ÷ (π × drill diameter in mm).
How do I calculate drilling feed? Multiply spindle RPM by feed per revolution. For example, 800 RPM × 0.10 mm/rev = 80 mm/min.
Why does a larger drill need lower RPM? The cutting edge travels a larger distance during every revolution, so RPM must decrease to maintain the selected cutting speed.
Is carbide always better than HSS? Not necessarily. Carbide can permit higher cutting speeds, but it generally benefits from a rigid machine and suitable operating conditions.
Should stainless steel be drilled at the same speed as mild steel? Generally no. Stainless grades often require more conservative cutting speeds and careful chip evacuation.
Does drill coating affect speed? Yes. Coating and drill geometry can change recommended cutting parameters, so manufacturer data should take priority.
Can this calculator determine the exact feed for every drill? No. Feed depends on drill diameter, geometry, material, machine rigidity, coolant and manufacturer recommendations.
What if my machine cannot reach the calculated RPM? Use the nearest practical machine speed while keeping the drilling conditions conservative and within the tool manufacturer's recommendations.