Surface Finish Calculator
Calculate expected surface roughness (Ra) from feed rate and tool nose radius for turning and milling operations.
Inputs
IPM
RPM
in
Results
Surface Roughness (Ra)
100.8 μin
Ra (metric)2.56 μm
Rz (peak-to-valley)403.2 μin
Feed per Revolution0.01 in/rev
Surface GradeN8
How to Use This Calculator
- Enter the programmed feed rate (IPM) and spindle speed (RPM) for the finishing pass.
- Set the tool nose radius (in or mm) from the insert or end-mill specification.
- Review theoretical surface roughness Ra (µin and µm), Rz peak-to-valley, and surface grade (N-number).
- Reduce feed rate or increase nose radius to achieve a finer surface finish.
- Compare the resulting Ra to your drawing's surface finish callout to verify compliance.
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