Drilling speed calculator
Calculate the appropriate speed for your HSS twist drill based on material and diameter. The calculator uses cutting speed as a basis and directly provides a reference value in revolutions per minute.
Recommended speed
Solid carbide drill setsFor higher speeds on the CNC machine
Note: All values are non-binding reference figures. Actual values depend on machine, tool, material and conditions. Start conservatively. No liability is accepted for tool breakage, machine damage or machining results.
What the Drilling Speed Calculator Computes
When drilling, it is not the diameter alone that determines the correct machine setting, but the cutting speed (vc) at the circumference of the drill bit. This depends on the material being machined. From this material-dependent cutting speed and the drill bit diameter, the calculator determines the appropriate spindle speed in revolutions per minute (rpm). The larger the diameter, the lower the spindle speed (for the same material).
Calculating Spindle Speed for Drilling: The Formula
The spindle speed is calculated from the cutting speed and the diameter:
n = (vc × 1000) / (π × d)
- n = spindle speed in rpm
- vc = cutting speed in m/min (material-dependent)
- d = drill bit diameter in mm
- The factor 1000 converts metres to millimetres
Guideline Values for Cutting Speed (HSS Twist Drill Bits)
| Material | vc in m/min |
|---|---|
| Wood | 100–250 |
| Plastic | 30–90 |
| Aluminium | 60–100 |
| Brass | 50–90 |
| Structural steel S235 | 30–40 |
| Stainless steel V2A/V4A | 8–14 |
Drill bits made from solid carbide can handle roughly two to three times these values.
How to Use the Calculator
Select the material and enter the drill bit diameter. The calculator applies a suitable cutting speed from the guideline range and outputs the spindle speed. If your machine does not match this value exactly, select the next lower adjustable step. This protects both the drill bit and the workpiece. Further tools can be found in the CNC calculator overview.
What You Should Watch Out For
- Stainless steel (V2A/V4A): cooling is required. Drill with a constant feed rate and do not let the drill bit rub, otherwise work hardening occurs and the material becomes hard.
- Large diameters: use a low spindle speed, as vc at the circumference would otherwise become too high.
- Guideline values remain guidelines: machine power, voltage and tool condition all influence the result.
For background on cutting data, read the BZT Knowledge Centre.
Spindle Speed Table: HSS Drill Bits from 2 to 12 mm
The table shows the spindle speed ranges (rpm) calculated from the cutting speeds for common drill bit diameters. The calculator at the top of the page gives intermediate sizes.
| Drill bit Ø | Wood | Plastic | Aluminium | Brass | Structural steel S235 | Stainless steel |
|---|---|---|---|---|---|---|
| 2 mm | 15,900–39,800 | 4,750–14,300 | 9,550–15,900 | 7,950–14,300 | 4,750–6,350 | 1,250–2,250 |
| 3 mm | 10,600–26,550 | 3,200–9,550 | 6,350–10,600 | 5,300–9,550 | 3,200–4,250 | 850–1,500 |
| 4 mm | 7,950–19,900 | 2,400–7,150 | 4,750–7,950 | 4,000–7,150 | 2,400–3,200 | 650–1,100 |
| 5 mm | 6,350–15,900 | 1,900–5,750 | 3,800–6,350 | 3,200–5,750 | 1,900–2,550 | 500–900 |
| 6 mm | 5,300–13,250 | 1,600–4,750 | 3,200–5,300 | 2,650–4,750 | 1,600–2,100 | 400–750 |
| 8 mm | 4,000–9,950 | 1,200–3,600 | 2,400–4,000 | 2,000–3,600 | 1,200–1,600 | 300–550 |
| 10 mm | 3,200–7,950 | 950–2,850 | 1,900–3,200 | 1,600–2,850 | 950–1,250 | 250–450 |
| 12 mm | 2,650–6,650 | 800–2,400 | 1,600–2,650 | 1,350–2,400 | 800–1,050 | 200–350 |
Calculated guideline values for HSS twist drill bits; in practice also limited by the maximum spindle speed of the machine or spindle. Solid carbide drill bits can handle approximately two to three times the spindle speed.
Frequently Asked Questions
How do I calculate the spindle speed when drilling?
Using the formula n = (vc × 1000) / (π × d). Here, vc is the material-dependent cutting speed in m/min and d is the drill bit diameter in mm. The result is the spindle speed in rpm.
What spindle speed do I need for stainless steel?
For stainless steel (V2A/V4A), the cutting speed with HSS twist drill bits is only 8–14 m/min, which is significantly lower than for steel. Cooling is required, and the drill bit must not rub, otherwise work hardening occurs.
Why does the spindle speed decrease with a larger diameter?
Because the cutting speed at the circumference should remain constant. Since the diameter is in the denominator of the formula, a larger drill bit automatically results in a lower spindle speed for the same material.
Do the values also apply to carbide drill bits?
No. The table provides guideline values for HSS twist drill bits. Drill bits made from solid carbide can handle approximately two to three times the cutting speed.
Is there a drilling speed calculator for other tools as well?
Yes. For milling cutters, use the cutting data calculator, and for taps, the thread feed calculator. An overview of all calculators can be found under CNC tools.
More CNC calculators
Looking for the right CNC gantry milling machine for your application? We are happy to advise you.