Spindle Speed Calculator

What is a Spindle Speed Calculator?

A spindle speed calculator helps you determine the correct rotational speed (RPM) and feed rate for milling, lathe, and CNC machining operations. It uses the cutting speed, workpiece or tool diameter, and tool parameters to calculate optimal spindle speed and feed rate for material removal processes like turning, facing, milling, and drilling.

How to Use the Spindle Speed Calculator

Using this calculator is straightforward:

1. Select your unit system - Metric (mm, m/min) or Imperial (in, ft/min).
2. Enter the diameter - The diameter of the workpiece for lathe operations or the tool diameter for milling.
3. Enter the cutting speed - The recommended cutting speed for the material being machined.
4. Enter the number of teeth - The number of cutting edges on the tool.
5. Enter the feed per tooth - The material removal per tooth per revolution.

The calculator instantly displays the spindle speed in RPM and the feed rate.

Spindle Speed Formula

The spindle speed is calculated using the following formula:

$$N_s = \frac{1000 \times V}{\pi \times D}$$

Where:

• $N_s$ = Spindle speed (RPM)
• $V$ = Cutting speed (m/min)
• $D$ = Diameter of workpiece or tool (mm)

For Imperial units, the formula becomes:

$$N_s = \frac{12 \times V}{\pi \times D}$$

The feed rate is calculated as:

$$F_r = N_s \times F_t \times Z$$

Where $F_t$ is the feed per tooth and $Z$ is the number of teeth.