A New Method of Certifying Standardized Rockwell Hardness Test Blocks
Samuel R. Low III, Walter S. Liggett Jr, David J. Pitchure
Rockwell hardness test blocks, whether standardized at the primary national laboratory level or by secondary commercial laboratories, have been certified historically by determining an average hardness value for the test surface of the block. However, because of the hardness non-uniformity of test blocks, measurement values will be dependent on where the indentations are made. Thus, a single certified average hardness value cannot completely characterize the hardness across the test surface of the block. The National Institute of Standards and Technology (NIST) has determing that the non-uniformity in the hardness of NIST test blocks varies smoothly across the surface of the block, and that the hardness variation can be modeled. This has led to the development of two types of hardness certifications which are provided to the customer: (1) the customary certified average HRC hardness across the test surface of the block; and (2) the additional certification of HRC hardness values at specific untestested locations on the test surface. The second type of certification provides the customer with a profile of how the hardness varies across the test surface of the customer's specific block, allowing the measurement uncertainty due to the non-uniformity of the test block to be reduced.
Proceedings of Hardmeko 98 International Symposium on Advances in Hardness Measurement
September 1, 1998
International Symposium on Advances in Hardness Measurement
certification, hardness, indentation, Rockwell hardness, standardization, test block, uniformity
, Liggett, W.
and Pitchure, D.
A New Method of Certifying Standardized Rockwell Hardness Test Blocks, Proceedings of Hardmeko 98 International Symposium on Advances in Hardness Measurement, Beijing, CH
(Accessed June 8, 2023)