Calibration Reproductibility Test for NIST's No. 3581 Standard Rockwell Diamond Indenter | NIST

Standard Rockwell diamond indenters play an important role for a worldwide unified Rockwell hardness scale. In 1994, the National Institute of Standards and Technology (NIST) established a Microform Calibration System with sufficiently small calibration uncertainty for the calibration of standard Rockwell indenters. In 1995, NIST established a group of Rockwell diamond indenters characterized both by high geometrical uniformity and hardness performance uniformity. One of them, No. 3581, was selected as the NIST’s primary Rockwell diamond indenter for the calibration of NIST’s Standard Reference Material (SRM) Rockwell C hardness blocks. This indenter was recalibrated in 1997 and 2005. The calibration results showed high stability for the microform geometry of the NIST’s standard Rockwell diamond indenter, as well as high calibration reproducibility for the NIST’s Microform Calibration System.