Spindle Speed Calculator (RPM)

Calculate the spindle speed (RPM) for milling and turning operations.

Parameters

Units

Cutting Speed (SFM)

Diameter (inches)

Calculated RPM

Ready to Calculate

Enter cutting speed and diameter to find the optimal RPM.

Overview

Spindle speed is the rotational frequency of the spindle of the machine, measured in revolutions per minute (RPM). Correct speed is crucial for tool life and surface finish.

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Pro Tips

Always start at the lower end of the recommended speed range.
Reduce speed if chatter (vibration) occurs.
Harder materials require slower cutting speeds.

Fun Facts

"SFM stands for Surface Feet per Minute."
"Carbide tools generally run at 2-3 times the speed of High Speed Steel (HSS)."
"Aluminum can be cut at much higher speeds than steel."

Formula: Imperial: RPM = (SFM × 3.82) / Diameter Metric: RPM = (m/min × 1000) / (π × Diameter)

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