As standardized in ISO2632/-1975 This set contains standards for the six most important maching methods in the prevalent "AA"values. These Surface Roughness is used to compare and deterrmine the degree of the surface finish by comparision method and eyeestimation or magnifying glass. The surface rough contrast blocks is made of 45 super carbor steel except the GCr15 which is using to plat lapping the block.
All 30 speciments are calibrated in y"AA(Arithmetical Average)and in the metric equivalents um Ra

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