Turning Surface Finish Calculator
Estimate turning surface roughness (Ra) from tool nose radius and feed per revolution to meet drawing requirements. Balance productivity and finish quality or debug poor finish with this quick tool.
Mode:
Input units:
Show results in:
mm/rev
mm
Formulas
Forward (Mode A) — compute Ra
Metric: Ra (µm) = 46 × Fn2 / r (Fn in mm/rev, r in mm)
Imperial: Ra (µin) = 31,675 × Fn2 / r (Fn in IPR, r in inch)
Inverse (Mode B) — compute Fn
Metric: Fn (mm/rev) = √( Ra × r / 46 )
Imperial: Fn (IPR) = √( Ra × r / 31,675 )