Roughness
Ra
μm
ISO 468
e 4287
0.006
0.012
0.025
0.05
0.1
0.2
0.4
0.8
1.6
3.2
6.3
12.5
25
50
100
200
AA
μinch
USA
ASA B.46.1
0.25
0.5
1
2
4
8
16
32
63
125
250
500
1000
2000
4000
8000
Ra μm
0.025
0.05
0.1
0.2
0.4
0.8
1.6
3.2
6.3
12.5
25
AA- CLA μinch
1
2
4
8
16
32
63
125
250
500
1000
50
2000
Roughness conversion table
Centre Line
Rz
Rt
Average
μm JIS
μm
CLA μinch
mean of 10
Germany
GB
points
BS 1134
4
8
16
32
63
125
250
500
1000
0.25
0.5
0.8
1.6
2.5
4
8
16
25
50
100
0.05
0.1
0.2
0.4
0.8
1.6
3.2
6.3
12.5
25
50
100
200
400
Ry
μm
max
height
0.05
0.1
0.2
0.4
0.8
1.6
3.2
6.3
12.5
25
50
100
200
400
UEFCO
fP
fP
fG
fF
fO
fO
fR
fT
ISO
1302
N01
N0
N1
N2
N3
N4
N5
N6
N7
N8
N9
N10
N11
N12
N13
N14
MCC
f5
f4
f3
f2
f1
f
Symbols and level of finishing
Conventional symbols
~
~
Surface description
Superfinishing
Burnishing diamond paste
Lapped, high level of finish, perfectly smooth
Lapped for seal joints
Ground, electric spark machining
Extra fine for machine tools, finish to the papers
Very smooth for machine tools
Smooth for machine tools
Medium for machine tools
Coarse for machine tools
Raw material
Raw material
- Roughness is the series of micro-geometrical errors present
on a surface prepared with any machining process.
- Roughness is measured on the surface in a transversal
direction to the main grooves.
- The mean arithmetical value “Ra” in μm is assumed for the
roughness measurement.
- Rt = maximum value of roughness or height from the lowest
point to highest point
- Rz = average roughness in 10 points