Stepover calculator finds the maximum lateral step distance for a ball-nose end mill that keeps scallops between passes below a target height, for 3D or surface finishing toolpaths.
Find the maximum stepover for a ball nose tool that keeps the scallop (cusp) height under a target finish tolerance.
Stepover = 2 x sqrt(R^2 – (R – h)^2), where R = D/2 and h = target scallop height.
How it works
A ball nose tool leaves a curved cusp between adjacent passes. The stepover that keeps that cusp below a target height is set by the tool radius and the height itself, geometry only, independent of feed or speed.
FAQ
What scallop height should I target? 0.0005 in (about 0.0127 mm) is a common fine-finish target; rough passes can use much larger values.
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How it works
A ball-nose cutter leaves a small ridge (scallop) between adjacent passes because its rounded tip doesn’t cut a flat surface; the closer together the passes, the shorter that scallop, and the smoother the resulting surface. Tighter scallop height targets require smaller stepovers, which increases toolpath length and machining time.
FAQ
What scallop height should I target? For a good as-milled finish before hand-polishing, 0.0005 to 0.001 in scallop height is common; roughing passes can tolerate much larger scallops, 0.005 in or more, since they’ll be removed by a finishing pass.
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