History of Nist Rockwell Test Block Standards

In 1991, NIST began the development of a national Rockwell hardness standardization laboratory at the urging of the ASTM and U.S. industry. The goals of this program are to standardize the Rockwell hardness scales for the United States and to provide industry with stable national transfer standards in the form of reference test blocks. In standardizing the Rockwell hardness scales, NIST has employed instruments and procedures having the highest metrological accuracy possible.

In June, 1998, NIST released the first Rockwell hardness reference test block standards for sale to industry. These blocks are for the HRC scale, at three hardness levels, nominally 25, 45 and 63 HRC. They are primarily used for use by the secondary Rockwell hardness calibration laboratories.

The next Rockwell scale for which NIST will release test blocks is the Rockwell B scale, likely followed by HRA, HRN and HRT scales. Eventually NIST hopes to provide a means for traceability to all Rockwell scales.