Method
Equation
h = R − √(R² − (p/2)²)Ra = arithmetic mean of the ideal circular profileTarget mode numerically solves Ra(p) for pitch pMachining
Surface Finish Calculator — Ball Nose Scallop & Turning Ra
Choose ball-nose milling or turning, enter the stock tool radius and required Ra, and Dimvo solves for maximum geometric stepover or feed per revolution. Expert mode checks a pitch you already know.
Decimal points and decimal commas are accepted.
Stock ball diametersmm
Maximum geometric pitch
Maximum stepover
0.3531 mm
Theoretical Ra
0.8 µm
Cusp height
3.118 µm
Stepover
0.3531 mm
Tool radius
5 mm
This is the ideal geometric limit, not a guaranteed measured finish. Use a smaller pitch to leave margin for runout, wear, chatter, deflection, material behaviour and measurement filtering.
Quick use
How to use this calculator
- Choose ball-nose milling or turning and whether to meet a target or inspect a current cut.
- Enter the ball diameter or insert nose radius and the drawing Ra.
- Use a smaller pitch than the geometric maximum to leave room for real process effects.
Limits
Assumptions
- Ideal circular tool profile
- Flat/even pass spacing
- No runout, wear, vibration, deflection or material effect
Provenance
Independent calculation
Generated from the displayed equation and user inputs. This page does not reproduce a standard or third-party table.
Common questions
Frequently asked questions
Is theoretical Ra the same as measured Ra?
No. The calculator isolates tool-path geometry. Measured roughness also includes runout, vibration, deflection, material response, wear and measurement filtering.
How do I reduce ball-nose scallop height?
Reduce stepover or use a larger ball radius. The calculator can solve the geometric result before you choose a CAM tool-path setting.