Spindle Speed

The rotational speed of the machine spindle, measured in RPM (revolutions per minute). It determines how fast the cutting tool or workpiece rotates during machining.

Spindle speed is a fundamental CNC parameter that must be correctly set for every machining operation.

Calculating Spindle Speed

The standard formula is:

N = (Vc × 1000) / (π × D)

Where:

  • N = Spindle speed (RPM)
  • Vc = Cutting speed (m/min)
  • D = Tool diameter (mm)

Key Considerations

  • Machine limits: Every CNC machine has a maximum spindle speed. High-speed machining centers can reach 20,000-60,000 RPM.
  • Tool balance: At high RPMs, tool balance becomes critical to prevent vibration and premature bearing wear.
  • Material dependency: Harder materials require lower cutting speeds, resulting in lower RPM for the same tool diameter.

Calculate the optimal spindle speed for your setup with our Feed & Speed Calculator.

Related Terms

Feed RateCutting SpeedSurface SpeedChip Load