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SURFACE TEXTURE (FINISH)

Surface texture Ra is a measurement of the average distance between the median line of the surface profile and its peaks and troughs

The relevant English standard is BS1134- Assessment of surface texture. (measurement units mm (micro.m))

ANSI B46.1 is used in USA (measurement units minch(micro.inch) )

The ISO standard is DIN ISO 1302 which uses N numbers .

Rules of Thumb for surface finish

• 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))

Sites Providing Information on surface Finish..

1. iCrank...A link to further information on Surface Texture
2. fedgage...An article on surface finish and its measurement
3. Taylor Hobson...Metrology Instruments- Useful information on FAQ link
4. Quality Mag...Aticles on surface texture measurement etc
5. Cyberman Quality and Design Page... Quality Online is a Site devote to quality management and measurement
6. Ultra Tecusa... Notes on measurement of surfaces http://www.ultratecusa.com/note&art/evalutng.htm

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Send Comments to RoyBeardmore@ic24.net

Last Updated 24/07/2003