SINAMA MACHINE
CUSTOM MACHINING SERVICE
Metal Material Composition
Metal Standard Conversion
Steel Hardness Conversion
Hardness & Tensile Conversion
Surface Roughness Conversion
Surface Roughness Conversion

The inch Ra roughness can be divided by 40 to get the metric Ra number. For example, if the inch drawing specifies surface roughness 32.
32 / 40 = Ra 0.8

Surface roughness can be specified in different ways. Below is a conversion table of them.

Ra Rmax(Ry) Rz Number Triangle
0.013a
0.025a
0.05a
0.10a
0.20a
0.05S
0.1S
0.2S
0.4S
0.8S
0.05Z
0.1Z
0.2Z
0.4Z
0.8Z
N 1
N 2
N 3
N 4
 VVVV
0.40a
0.80a
1.6a
1.6S
3.2S
6.3S
1.6Z
3.2Z
6.3Z
N 5
N 6
N 7
 VVV
3.2a
6.3a
12.5S
25S
12.5Z
25Z
N 8
N 9
 VV 
12.5a
25a
50S
100S
50Z
100Z
N10
N11
 


 
 
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