CopperFusion

Lathe Speeds and Feeds Calculator

Estimate a turning speed from surface cutting speed and workpiece diameter, then calculate the corresponding linear feed rate. Values are metric and intended for conventional lathe turning.

Cutting inputs
Choose a material to load a broad starting speed, or choose custom and enter a recommended cutting speed below.
Used to select a material preset only. Tool material is disabled when you choose a custom cutting speed.
The material choices provide broad workshop starting values. Replace this with your tooling manufacturer’s recommendation where available.
Shown with the result as an operation check. It does not directly change the RPM or feed-rate formulas.

Calculated starting point

Turning settings

Spindle speed
764 RPM
Feed rate
115 mm/min

Based on 120 m/min at 50 mm diameter, 0.15 mm/rev feed and 1 mm radial depth of cut.

How the calculation works

Cutting speed is the surface speed where the tool meets the rotating workpiece. Because a larger diameter travels farther in each revolution, it needs a lower spindle speed to maintain the same cutting speed.

Spindle speed (RPM)(cutting speed × 1000) ÷ (π × diameter)

Linear feed rate is the distance the tool advances per revolution multiplied by spindle speed.

Feed rate (mm/min)RPM × feed per revolution

Using the result at the lathe

  • Choose the nearest available spindle speed without exceeding the machine or chuck limit.
  • Start conservatively when the material grade, tool geometry or workholding is uncertain.
  • Reduce speed for interrupted cuts, long overhangs, poor rigidity or heat-sensitive setups.
  • Watch chip formation, sound, finish, cutting forces and tool temperature, then adjust one setting at a time.
  • Depth of cut affects cutting load and required power even though it is not part of these two equations.