Turning Time Calculator

Work out turning time instantly with clear inputs, formula shown and shareable results.

About Turning Time Calculator

On a lathe the carriage advances by the feed per revolution each turn, so feed rate is rpm times feed per revolution and time is length divided by that. Cutting speed is shown alongside because it falls as the diameter is reduced, so a constant rpm gives a slower cut on each successive pass.

Formulas

Feed rate

IPM = rpm x feed per revolution

Turning time

T = length / IPM; SFM = pi x D x rpm / 12

Worked example

With the default values below, Turning Time Calculator returns Turning time per pass of 1.333. Change any input above and every figure here is recalculated in your browser.

Inputs used

Length to turnminimum 0.01 in: 8 in
Workpiece diameterminimum 0.01 in: 2 in
Spindle speedminimum 1 rpm: 600 rpm
Feed per revolutionminimum 0 in/rev: 0.01 in/rev

Results

Turning time per pass: 1.333 min
Turning time per pass: 80.0 s
Carriage feed rate: 6.000 in/min
Cutting speed at this diameter: 314.2 SFM

Step by step

1Values used
2Feed rate
3Turning time
4Turning time per pass= 1.333 min
5Turning time per pass= 80.0 s
6Carriage feed rate= 6.000 in/min
7Cutting speed at this diameter= 314.2 SFM

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Turning Time figure worked out?

IPM = rpm x feed per revolution. On a lathe the carriage advances by the feed per revolution each turn, so feed rate is rpm times feed per revolution and time is length divided by that.

What is constant surface speed mode?

The control raises rpm as the diameter shrinks to hold cutting speed constant, which keeps tool life and finish uniform from the outside of a facing cut to the centre.

What values do I need to enter?

This calculator takes 4 inputs: Length to turn, Workpiece diameter, Spindle speed, Feed per revolution. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.