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Lathe RPM and feed calculator
Use the workpiece diameter at the cutting location. A fixed RPM gives a different surface speed as diameter changes. Constant surface speed mode also needs a machine-specific maximum RPM and safe workholding limit.
Formula and inputs
RPM = 1000 × Vc / (π × D); feed = RPM × feed per revolution.
Worked example
At 50 mm diameter and 150 m/min the theoretical speed is about 955 RPM. A 0.2 mm/rev feed gives 191 mm/min.
Use the result in your setup
Confirm the input dimensions and unit system against your drawing before calculating. Keep full precision during a calculation and round only the final value to suit the measurement or programming requirement. A numerical result does not account for a machine’s complete setup, workholding or control configuration.