Every tool and material has a recommended cutting speed – the surface speed at which the cutting edge moves through the work. Turning that into spindle RPM requires the diameter: small tools must spin much faster than large ones for the same surface speed. The feed rate then follows from the chip load per tooth and the number of cutting edges.
How to use the Spindle Speed Calculator
- Cutting speed
- Tool / workpiece diameter
- Number of teeth (flutes)
- Feed per tooth (chip load)
- Every result field is editable: type into Spindle speed and Cutting speed plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the cutting speed for your tool and material, the tool (or workpiece) diameter, the number of teeth and the feed per tooth. Type an RPM into the result to see the cutting speed.
Tips for an accurate estimate
- Keep units consistent – the calculator handles conversions, but check every field’s unit before reading a result.
- Use values from standards, data sheets or test pieces whenever you have them; typical values are only a starting point.
- Apply appropriate safety factors and have structural, electrical and pressure work checked by a qualified professional.
- Record the inputs you used so the calculation can be reviewed later.
Common mistakes to avoid
- Confusing diameter and radius, or nominal and actual sizes.
- Using allowable stresses and ultimate strengths interchangeably.
- Treating rule-of-thumb results as a substitute for code tables or an engineered design.
Inputs explained
| Field | What to enter |
|---|---|
| Cutting speed | Units: m/min, ft/min (SFM), m/s |
| Tool / workpiece diameter | Units: mm, in, cm |
| Number of teeth (flutes) | A number |
| Feed per tooth (chip load) | Units: mm, in |
What each result means
- Spindle speed = [Cutting speed]÷(pi×[Tool ÷ workpiece diameter])×60
- Feed rate = [Spindle speed]÷60×[Feed per tooth (chip load)]×[Number of teeth (flutes)]
Example values
How the main result changes when Cutting speed changes and everything else stays at the example values above:
| Cutting speed (m/min) | Spindle speed (rpm) |
|---|---|
| 50 | 1,592 |
| 75 | 2,387 |
| 100 | 3,183 |
| 125 | 3,979 |
| 150 | 4,775 |
| 200 | 6,366 |
Formula
N (rpm) = 1000 × Vc ÷ (π × D) (Vc in m/min, D in mm)N = 12 × SFM ÷ (π × D) (D in inches)Feed rate vf = N × fz × ZWorked example
Inputs — Cutting speed: 100 m/min; Tool / workpiece diameter: 10 mm; Number of teeth (flutes): 4; Feed per tooth (chip load): 0.05 mm.
Results — Spindle speed = 3,183 rpm; Feed rate = 636.6 mm/min.
Frequently asked questions
What spindle speed for a 10 mm end mill in steel?
At 100 m/min: 1000 × 100 ÷ (π × 10) ≈ 3,180 rpm.
What cutting speed should I use?
Carbide in mild steel 100–250 m/min, in aluminium 300–1,000 m/min; HSS tools roughly a quarter of that. Use the tool maker's data.
What is chip load?
The thickness of material each tooth removes per revolution – too low rubs and work-hardens, too high breaks tools.
What formula does the Spindle Speed Calculator use?
N (rpm) = 1000 × Vc ÷ (π × D) (Vc in m/min, D in mm).