Surface Texture Index Page

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 BS 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

μm = 10 -6 metre
μinch = 10 -6 inch

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
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
Finish   Lapping/Superfinishing Ground Finishes Smooth Turned Medium Turned Rough Machined

Rules of Thumb for surface finish equivalent of N grade and Ra values

Sites Providing Information on surface Finish
  1. iCrank...
  2. A link to further information on Surface Texture
  3. Bright Burnishing Tools Private Ltd.... Lots of useful relevant information on one page
  4. MD metric Surfruff... Everything you need to know on one page
  5. Hallite UK - Surface Roughness... Useful Notes.

Surface Texture Index Page