Machining and Fastener Charts

Lathe RPM, feed and time.

Enter the cutting speed the tool maker gives for your material, the diameter you are turning and the feed per revolution. You get spindle RPM and feed per minute, plus cutting time and metal removal rate if you add the length and depth of cut. Runs in your browser; nothing is sent or stored.

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Inputs

m/min or ft/min. Take it from the insert or tool maker for your material.

mm or in. The diameter at the cutting tool.

mm/rev or in/rev.

mm or in; needed for removal rate.

mm or in; needed for cutting time.

Result

Fill the form and press Calculate.

Answer first. Spindle speed n = cutting speed x 1000 / (pi x diameter) with mm and m/min, or cutting speed x 12 / (pi x diameter) with inches and ft/min. Cutting time for a pass = length / (feed per rev x n).

Worked example

Turn a 50 mm bar at 200 m/min with a 0.2 mm/rev feed. n = 200 x 1000 / (pi x 50) = 1273 rpm. Feed per minute = 0.2 x 1273 = 255 mm/min. A 100 mm long cut takes 100 / (0.2 x 1273) = 0.393 min, about 24 seconds. At 2 mm depth of cut the metal removal rate is 200 x 2 x 0.2 = 80 cm³/min.

How it works

Cutting speed is an input. The right cutting speed depends on the material, tool, coolant and tool life you want. Take it from the tool maker's catalogue. This tool does not guess it.

Constant speed. Normally the cutting speed is held constant, so RPM changes as the diameter changes. On a lathe without constant surface speed control, work out RPM for the diameter you are cutting.

Removal rate. Q = vc x ap x fn gives cm³/min in metric. With inches the formula is multiplied by 12, giving in³/min.

Safety. Check the RPM against the maximum for the chuck, the work and the machine, and the work's length-to-diameter ratio. These are general formulas, not machining advice for a specific job.

Sources

Spindle speed, machining time and metal removal rate are the Sandvik formulas; feed per minute is feed per revolution times spindle speed.

FAQ

How do I calculate lathe RPM?

RPM = cutting speed (m/min) x 1000 / (pi x diameter in mm). In inches, RPM = cutting speed (ft/min) x 12 / (pi x diameter in inches).

How do I calculate cutting time on a lathe?

Time in minutes = length of cut / (feed per revolution x RPM).

What cutting speed should I use?

Use the value from your tool or insert maker for the material you are cutting. This calculator takes the number you give it and does not recommend one.

What diameter do I use when facing?

The diameter at the tool changes through a facing cut, so the RPM for a given cutting speed changes with it. Work out RPM for the diameter you are cutting at, and stay under the maximum RPM of the machine and chuck.

What is feed per revolution?

It is how far the tool advances along the work for each turn of the spindle, in mm/rev or in/rev.

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