Scallop / Stepover
Optimize your 3D surfacing toolpaths by balancing surface finish (scallop height) against machining time (stepover).
The Surface Finish Tradeoff
When surfacing a 3D contour with a ball endmill, the tool leaves behind tiny ridges of unmachined material between each pass. These ridges are called scallops (or cusps).
To reduce the scallop height (improving surface finish and reducing hand-polishing time), you must reduce the stepover distance. However, halving the stepover distance doubles the machining time. This calculator helps you find the exact mathematical point of diminishing returns.
Rule of Thumb:
To maintain the same scallop height, if you use a larger diameter tool, you can significantly increase your stepover. Always use the largest ball endmill the geometry will allow.