Core CNC machining formulas

Use cutting data recommended by the tool maker for the actual tool, material and operation. Spindle speed: n = 1000 × Vc ÷ (π × D), where Vc is cutting speed in m/min and D is diameter in mm. In milling, table feed Vf = fz × z × n; in turning, Vf = f × n. Approximate cutting time is cutting length divided by feed rate.

Worked example

At 60 mm diameter and 100 m/min, n ≈ 531 rpm. fz is feed per tooth and z is the number of teeth. Check tool data, machine speed limits, workholding and a safe first run before production.