Turning Feed Calculator

LATHE

Turning feed rate converts spindle RPM and a chosen feed per revolution into the linear feed rate (IPM) the lathe carriage moves during a cut.

Feed Rate—
Feed Rate (IPM) = RPM × Feed per Revolution.

How it works

Lathe feed is programmed per spindle revolution rather than per tooth because a turning tool has a single continuous cutting edge, not multiple flutes like a mill. Feed per revolution is chosen based on tool nose radius, desired surface finish, and material; finer feeds leave a smoother finish but take longer per pass. Doubling RPM at a fixed feed per revolution doubles the resulting feed rate in inches per minute, which is why feed per revolution, not feed rate directly, is the value most machinability data and tooling charts are built around.

FAQ

What feed per revolution should I start with? For general roughing in steel with a standard-radius insert, 0.008 to 0.015 in/rev is a common starting range; finishing passes often drop to 0.002 to 0.006 in/rev for a better surface finish.

Related Guides

CNC Calculators · Turning RPM Calculator · Feed per Revolution Calculator

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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.