Drill Speed Calculator
Enter the drill diameter and your material's recommended cutting speed, and get the spindle RPM to run the drill press or mill at.
Typical drilling speeds, HSS twist drill (SFM)
| Material | SFM |
|---|---|
| Aluminum | 250–300 |
| Brass | 150–300 |
| Mild steel (1018) | 80–100 |
| Alloy steel (4140) | 50–70 |
| Stainless steel (304) | 40–60 |
| Cast iron | 70–90 |
Carbide-tipped or solid carbide drills typically run 3–5× faster than these HSS numbers.
Same formula as milling, different typical numbers
Drilling uses the identical RPM = (SFM × 12) ÷ (π × diameter) relationship as milling or turning — the geometry of converting a surface speed to a rotational speed doesn't care what the operation is. What changes is the typical SFM range: a twist drill's chisel edge doesn't cut as efficiently as a milling cutter's edges, so drilling SFM numbers usually run lower than milling SFM for the same material and tool material.
Why drills need more RPM headroom at small diameters
A #60 drill (0.040 in) at 90 SFM calls for over 8,000 RPM — well past what most manual drill presses or mills can turn. In practice, small-diameter drilling is usually limited by the machine's top speed rather than the ideal SFM, which is why small holes often get drilled slower than the "correct" number would suggest, relying on a sharp drill and steady feed rather than exact speed to get a clean hole.
Peck drilling deeper holes
This calculator gives you the RPM, not the feed strategy — holes deeper than about 3× the drill diameter usually need peck drilling (retracting periodically to clear chips) rather than a single continuous plunge, since a twist drill's flutes can only carry chips out so far before they pack and either break the drill or push it off-center.