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Capability in Rockwell C Scale Hardness



Walter S. Liggett Jr, Samuel Low, David J. Pitchure, Jun-Feng Song


A measurement system is capable if it produces measurements with uncertainties small enough for demonstration of compliance with product specifications. To establish the capability of a system for Rockwell C scale hardness, one must assess measurement uncertainty and, when hardness is only an indicator, quantify the relation between hardness and the product property of real interest. 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 test blocks that NIST issues as Standard Reference Materials (SRMs). The important innovation introduced in this paper is improved handling of the hardness variation across test-block surfaces. In addition to hardness itself, the methods in this paper might be applicable to other local measurement of a surface.
Journal of Research of the National Institute of Standards and Technology


calibration, critical to product quality, experimental design, indentation hardness, measurement system comparison, spatial statistics, standard reference material, surface measurement, test method, trend elimination, uncertainty component


Liggett Jr, W. , Low, S. , Pitchure, D. and Song, J. (2000), Capability in Rockwell C Scale Hardness, Journal of Research of the National Institute of Standards and Technology, [online], (Accessed April 18, 2024)
Created June 30, 2000, Updated October 12, 2021