Lathe · OD/ID turning
Turning Calculators
Speed, feed, metal removal rate, theoretical surface finish and cycle time for OD/ID turning operations. All formulas shown so you can verify against your machining handbook.
Cutting speed → RPM
n = Vc·1000 / (π·D)Metal removal rate
Q = Vc · ap · fnTheoretical surface finish
Ra = fn² / (32·r)Feed for a target Ra
fn = √(32·r·Ra)Machining time
t = L·passes / (fn·n)Formulas used
Metal removal rate: Q (cm³/min) = Vc (m/min) × ap (mm) × fn (mm/rev)
Theoretical Ra: Ra (µm) = fn² / (32 × r) × 1000 — fn and r in mm
Machining time: t (min) = cut length × passes / (fn × n)
Frequently asked questions
How do I calculate metal removal rate in turning?
Q = cutting speed × depth of cut × feed per revolution. With Vc in m/min and ap, fn in mm, the result is directly in cm³/min.
What surface finish will I get from a 0.8 mm nose radius?
At a feed of 0.2 mm/rev, theoretical Ra = 0.2²/(32×0.8)×1000 ≈ 1.56 µm. Real finish depends on tool wear, built-up edge and vibration, so treat it as a best-case floor.
Does depth of cut affect surface finish in turning?
Not directly in the theoretical model — finish is governed by feed and nose radius. In practice, heavier depths raise cutting pressure and can degrade finish through deflection.