Hard facts
Theory of hardness testing
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The hardness of carbon and graphite materials is determined according to the DIN 51917 standard. The DIN 51917 standard defines the procedure for determining the Rockwell hardness. The test method described in this standard is a modified Rockwell test method for testing carbon materials with balls in accordance with ISO 6508-1. The Rockwell hardness of metal-graphite materials, e.g. carbon brushes in motors and generators, can also be determined using this method.
