Engineers Edge Surface Roughness Conversion Chart - Engineers Edge

Surface Roughness Conversion Chart

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Surface Roughness Review
Surface Roughness Standards Comparator

Where:

Ra = Roughness, average in micro-meters & micro-inches
RMS = Root Mean Square in micro-inches
CLA = Center Line average in micro-inches
Rt = Roughness, total in microns
N = New ISO (Grade) Scale numbers
Cut-Off Length = Length required for sample.

Conversion math at bottom --

Surface Roughness Conversion Chart
Ra
micro-meters
Ra
micro-inches
RMS
CLA
(N)
Rt
N
Cut-Off Length
in.
mm
0.025
1
1.1
1
0.3
1
0.003
0.08
0.05
2
2.2
2
0.5
2
0.01
0.25
0.1
4
4.4
4
0.8
3
0.01
0.25
0.2
8
8.8
8
1.2
4
0.01
0.25
0.4
16
17.6
16
2.0
5
0.01
0.25
0.8
32
32.5
32
4.0
6
0.03
0.8
1.6
63
64.3
63
8.0
7
0.03
0.8
3.2
125
137.5
125
13
8
0.1
2.5
6.3
250
275
250
25
9
0.1
2.5
12.5
500
550
500
50
10
0.1
2.5
25.0
1000
1100
1000
100
11
0.3
8.0
50.0
2000
2200
2000
200
12
0.3
8.0

Conversions (math):

CLA (micro inches) = Multiply Ra(µm) x 40

RMS * (acceptable 1.1 - 1.7 factor) = Multiply CLA x 1.1

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