Gogan hardness, a nondestructive (a penetrator causes shallow surface deformation) method of measuring compressibility, is used as a quality control check of the consistency of formulation and processing of brake lining. Gogan hardness alone shows nothing about a lining’s ability to develop friction or to resist fade when used as a friction element in brakes. Gogan hardness varies with formulation, contour, and thickness of the lining. The hardness of sintered powder metal lining is usually determined with Rockwell Superficial hardness equipment. Reference ASTM B 347 ¹ (latest revision) “Standard Method of Test for Hardness of Sintered Metal Friction Materials.” The Gogan hardness and the range of Gogan hardness are peculiar to each formulation, thickness, and contour and, therefore, the acceptable values or range must be established for each formulation and part configuration by the manufacturer.