Surface Texture Equivalents
ANSI B46.1 is used in USA (measurement units minch(micro.inch) )
ISO 1302:1992 which uses N numbers..These are not included in EN ISO 1302:2002
The table below provide equivalent values for the Average Roughness R a , the USA R a Values, the approximate R t values, the N numbers, the obsolete triangular representations, and some manufacturing finishes. There is no mathematical relationship between R a and R t The R t values shown in the table below are very approximate and should only be used for guidance. For notes describing the meanings of R a, R t etc. reference links below and surface finish.
Notes:
μm = 10 -6 metre
μinch = 10 -6 inch
| R a-μm - |
0.025 |
0.05 |
0.1 |
0.2 |
0.4 |
0.8 |
1.6 |
3.2 |
6.3 |
12.5 |
25 |
50 |
| R a- μinch |
1 |
2 |
4 |
8 |
16 |
32 |
63 |
125 |
250 |
500 |
1000 |
2000 |
| R t (R y ) -μm |
|
0,25 |
0,5 |
1 |
2 |
4 |
8 |
16 |
32 |
|
|
|
| N-Grade |
N1 |
N2 |
N3 |
N4 |
N5 |
N6 |
N7 |
N8 |
N9 |
N10 |
N11 |
N12 |
Triangular
Indication |
 |
 |
 |
 |
| Finish |
|
Lapping/Superfinishing |
Ground Finishes |
Smooth Turned |
Medium Turned |
Rough Machined |
|
Rules of Thumb for surface finish equivalent of N grade and Ra values
-
Rough turned with visible toolmarks....N10 = 12.5mm (micro.m)
-
Smooth machined surface....N8 = 3.2mm (micro.m)
-
Static mating surfaces (or datums).... N7 = 1.6mm(micro.m)
-
Bearing Surfaces.... N6 = 0.8mm (micro.m)
-
Fine lapped surfaces.... N1 = 0.025mm (micro.m)
|
