Turning speeds and feeds (RPM, feed rate, theoretical roughness)
Spindle speed, feed rate and cutting time for OD turning, plus the theoretical surface roughness from feed and nose radius.
◎Turning calculator
Spindle speed n—rpm
Feed rate Vf—mm/min
Cutting time—
Theoretical roughness Rz—µm
Theoretical Ra (approx.)—µm
n = 1000 × Vc ÷ (π × D) Vf = f × n Time = L ÷ Vf Rz = f² ÷ (8 × r) × 1000 Ra ≈ Rz ÷ 4
Red = input dimensions, green = rotation and motion. Schematic, not to scale.
Notes
- Theoretical roughness depends only on the tool geometry. Real roughness is larger because of chatter, built-up edge and tool wear.
- With constant surface speed (G96) the spindle speeds up as the diameter gets smaller. Always set a maximum spindle speed (G50 or equivalent).
All values are guides. Start from the tool maker’s recommended cutting data and adjust for your machine, workholding and coolant. Calculations run in your browser; nothing you enter is sent anywhere.