spex 50 cc ball mill. Fundamentals of Rockwell Hardness Testing · penetrator scales and 130 on the ball penetrator scales. One regular Rockwell number represents a penetration of 0.002 mm (0.000080 inch). Therefore a reading of C60 indicates penetration from minor to major load of (100 to 60 Rockwell points) x 0.002 mm = 0.080 mm or 0.0032 inch.
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