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Calcimator

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
  1. Enter the programmed feed rate (IPM) and spindle speed (RPM) for the finishing pass.
  2. Set the tool nose radius (in or mm) from the insert or end-mill specification.
  3. Review theoretical surface roughness Ra (µin and µm), Rz peak-to-valley, and surface grade (N-number).
  4. Reduce feed rate or increase nose radius to achieve a finer surface finish.
  5. Compare the resulting Ra to your drawing's surface finish callout to verify compliance.

How the result changes with Spindle Speed

Spindle SpeedSurface Roughness (Ra)
3,09095 μin
10,5658.1 μin
19,5352.4 μin
27,0101.2 μin

What each input means

Feed Rate
Programmed feed rate in inches per minute.
Spindle Speed
Spindle rotation speed.
Tool Nose Radius
Insert or tool nose radius (e.g., 1/32" = 0.031").

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    Feed Rate = 30, Spindle Speed = 3000, Tool Nose Radius = 0.031 = 3 input(s) provided
  2. Calculate Surface Roughness
    Surface Roughness
    100.8 = 100.8
  3. Calculate Ra
    Ra
    2.56 = 2.56
  4. Calculate Rz
    Rz
    403.2 = 403.2

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