Drill Press Speed (RPM) Calculator
Calculate correct drill press RPM from bit diameter, material type, and surface cutting speed.
Returns optimal RPM for steel, aluminum, wood, and plastics.
Running a drill press at the correct RPM is critical for clean holes, long tool life, and safe operation. Too fast and the bit overheats, dulls prematurely, or grabs the workpiece. Too slow and the drill rubs instead of cutting, causing work hardening in metals like stainless steel.
The Fundamental Formula
RPM = (Cutting Speed × 1000) / (π × Drill Diameter)
Or equivalently:
RPM = (CS × 318.31) / D
Where:
- CS = Cutting speed in meters per minute (m/min), determined by the workpiece material and drill bit type
- D = Drill bit diameter in millimeters
- 318.31 = 1000/π (conversion constant)
Cutting Speed Reference Table (HSS Drill Bits)
| Material | Cutting Speed (m/min) | Notes |
|---|---|---|
| Mild Steel | 25–35 | Most common workshop material |
| Stainless Steel | 10–15 | Use cutting fluid, steady feed |
| Aluminum | 60–100 | Use high RPM, clear chips often |
| Brass | 40–60 | Self-feeding, so reduce feed pressure |
| Cast Iron | 20–30 | Dry cutting OK, makes dust not chips |
| Copper | 40–60 | Similar to brass |
| Plastic/Acrylic | 30–50 | Slow feed to prevent melting |
| Wood (softwood) | 50–80 | Can run faster with brad-point bits |
| Wood (hardwood) | 30–50 | Slower to prevent burning |
Bit material multipliers
The table above is for plain high-speed steel. Harder bit materials tolerate more heat, so they run faster:
| Bit type | Multiplier | Why |
|---|---|---|
| HSS | 1.0 | The baseline every chart is quoted for |
| TiN coated HSS | 1.3 | Coating cuts friction and reflects heat back into the chip |
| Cobalt (M35/M42) | 1.25 | Red-hardness holds an edge hotter; the real gain is in stainless |
| Carbide-tipped | 2.0 | Runs 1.5–3× depending on rigidity; brittle, so it wants no chatter |
Carbide only earns its multiplier on a rigid machine. On a wobbly bench-top drill press a carbide bit chips before it wears, and a cobalt bit at 1.25× will outlast it.
Worked Example
Drilling a 10 mm hole in mild steel with an HSS bit (cutting speed 30 m/min):
RPM = (30 × 318.31) / 10 = 9549.3 / 10 = 955 RPM
On a typical drill press with fixed pulleys you cannot dial that in, so you pick the closest available step, probably 900 or 1000 RPM. When the nearest step falls outside the recommended range, go to the one below it. Running slow costs you time; running fast costs you the bit.
Feed Rate Guideline
Feed scales with the bit, not with the material alone, which is why a single thousandths-per-rev figure only ever fits one size of drill. A workable rule for steel is 0.01 to 0.02 mm per revolution for each millimetre of drill diameter:
| Drill diameter | Feed per revolution |
|---|---|
| 3 mm | 0.03–0.06 mm (0.001–0.002") |
| 6 mm | 0.06–0.12 mm (0.002–0.005") |
| 10 mm | 0.10–0.20 mm (0.004–0.008") |
| 16 mm | 0.16–0.32 mm (0.006–0.013") |
| 25 mm | 0.25–0.50 mm (0.010–0.020") |
Aluminum and brass take the top of each band, stainless the bottom. On a hand-fed drill press it all comes down to slow, steady downward pressure where the drill produces even curly chips. Not dust, and not large grabbing chips.
Drilling speeds sit below turning speeds for the same material, and that is not an inconsistency. A drill cuts with its whole lip inside a hole with nowhere for the heat to go, while a lathe tool cuts one point in open air. Mild steel at 25 to 35 m/min here is 82 to 115 SFM, which lines up with the 80 to 100 SFM the lathe cutting speed calculator recommends. Stainless is the one that separates: 10 to 15 m/min drilling against 50 to 80 SFM turning.
Peck Drilling
For holes deeper than 3× the drill diameter, use peck drilling: drill to 1× diameter depth, retract fully to clear chips, then advance again. This prevents chip packing, reduces heat, and extends bit life dramatically.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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