Surface Finish Calculator (Ra)

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This surface finish calculator estimates the roughness average (Ra) based on feed per revolution and tool nose radius.

Surface finish is strongly influenced by feed rate and tool geometry.

Formula:

Ra ≈ (Feed per revolution²) / (32 × Tool Nose Radius)

Lower feed rates and larger tool nose radius produce smoother finishes.

Example:

If feed = 0.010 in/rev and nose radius = 0.032 in:

Ra ≈ (0.010²) / (32 × 0.032) ≈ 98 microinches.

When to use this calculator:

Use this calculator to estimate surface roughness based on feed rate and tool geometry.

Machining tip:

Reducing feed rate or increasing tool nose radius can significantly improve surface finish.

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