To determine the capability of a system for Rockwell C scale hardness, one must make test measurements, which can be planned and interpreted as explained in this paper. Uncertainty, which is one part of capability, is treated specifically, and product specification limits, the other part, are covered more generally. The uncertainty involves several components, which we designate as lack of repeatability, lack of reproducibility, machine error and indenter error. Component-by-component assessment leads to understanding of mechanisms and thus to guidance on system upgrades if these are necessary. Assessment of some components calls only for good-quality test blocks, and assessment of others requires NIST SRM test blocks. The important innovation introduced is this paper is improved handling of the hardness variation across test-block surfaces.
Citation: Journal of Research (NIST JRES) -
Volume: 105 No. 4
NIST Pub Series: Journal of Research (NIST JRES)
Pub Type: NIST Pubs
calibration, critical to product quality, experimental design, indentation hardness, measurement system comparisons, spatial statistics, standard reference material, surface measurement, test method