Hardness measurements are used as a quality control check of the consistency of formulation and processing of brake linings. This hardness method is nondestructive. NOTE-This method is not a measure of friction level. The hardness and the range of hardness are characteristic of each formulation; therefore, the acceptable values and ranges must be established for each formulation and may be affected by processing. NOTE-The hardness of sintered powder metal lining is usually determined with Rockwell superficial hardness equipment. (See ASTM B 347)