Turning Calculator

How it works

1. 1Enter the workpiece diameter (mm), spindle speed (rpm), feed per revolution (mm/rev), and depth of cut (mm).
2. 2The calculator applies Vc = π·D·N÷1000 to find cutting speed, multiplies rpm × feed to get feed rate, then uses Vc·f·ap for MRR.
3. 3Results update instantly — adjust spindle speed or feed to hit a target surface speed or stay within your machine’s power envelope.

Use cases

• Setting up a CNC lathe program: verify cutting speed matches the insert manufacturer’s recommended Vc range before posting G-code.
• Manual machining: look up surface speed in ft/min to match an imperial speed chart when your lathe has an imperial RPM dial.
• Estimating cycle time: divide total volume to remove by the MRR (cm³/min) to get a rough machining time per part.

Frequently asked questions

Why is cutting speed calculated from the workpiece diameter and not the tool diameter?

In turning, the workpiece rotates and the single-point tool is stationary. The relative velocity at the cutting edge equals the surface speed of the part: Vc = π·D·N÷1000. Tool diameter is irrelevant — it is the part diameter D that sets the contact speed.

What is a realistic cutting speed for steel on a carbide insert?

Uncoated carbide on mild steel typically runs 100–200 m/min (330–660 ft/min). Coated inserts (TiAlN, TiCN) can reach 200–350 m/min. Example: a 60 mm bar at 1200 rpm gives Vc = π×60×1200÷1000 ≈ 226 m/min — suitable for a coated carbide grade.

How do I use MRR to estimate machining power?

Cutting power Pc ≈ MRR × kc ÷ 60 000 (MRR in cm³/min, kc in N/mm²). For mild steel kc ≈ 2000–2500 N/mm², so at MRR = 24 cm³/min the spindle needs roughly 0.8–1.0 kW of net cutting power — add 20–30 % for spindle losses to size your machine.