Surface Finish

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SURFACE TEXTURE Examples

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 Ra , the USA Values and the N numbers.. .

mm	0.025	0.05	0.1	0.2	0.4	0.8	1.6	3.2	6.3	12.5	25	50
minch	1	2	4	8	16	32	63	125	250	500	1000	2000
N-Grade	N1	N2	N3	N4	N5	N6	N7	N8	N9	N10	N11	N12
Finish	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)

Sites Providing Information on surface Finish..

Predev.com...Precision Devices. Chart of Machining vs surface Texture
iCrank... A link to further information on Surface Texture
Ultra Tecusa... Notes on measurement of surfaces

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Last Updated 07/04/2004