Estimate theoretical surface finish (Ra) from feed rate and tool nose radius.
Ra (μin)
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Ra (μm)
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Turning formula: Ra = f² / (32 × r) where f = feed/rev, r = nose radius Ball nose milling: Ra = (stepover)² / (32 × r) where r = ball radius
Note: This is theoretical surface finish. Actual finish depends on material, tool condition, rigidity, coolant, and cutting speed. Multiply by 1.5–2× for a realistic estimate.