CNC Spindle Speed Calculator
Enter your cutting speed, tool diameter and feed settings.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
This calculator finds the metric spindle speed for a CNC machine using RPM = (Vc × 1000) ÷ (π × D), where Vc is the recommended cutting speed for the material and tool in meters per minute, and D is the tool diameter in millimeters — a formula derived directly from the fact that surface speed is the tool's circumference times its rotational speed. It also computes the table feed rate as RPM × feed-per-tooth (fz) × number of teeth (z), which determines how fast the machine advances the workpiece.
CNC machinists and manufacturing engineers use these two numbers together to set up a milling operation correctly: spindle speed too high for the material overheats and dulls the cutting edge, while a feed rate too low relative to spindle speed causes rubbing instead of cutting — both shortening tool life. Cutting-speed values (Vc) come from tooling manufacturer charts and vary widely by material, from roughly 20-40 m/min for hardened steel to 200+ m/min for aluminum.
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