Which hardness testing methods are specified for rigid metal measures?

• A. Shore A hardness
• B. Mohs hardness
• C. Brinell or Rockwell hardness
• D. Vickers hardness

Answer: (C)

For rigid metal measures, the hardness test method chosen should be a macro-hardness approach that is well standardized and easy to apply to metal artifacts. Brinell and Rockwell hardness tests fit this need because they use defined loads and indenters to create clear, repeatable impressions on metal surfaces, and their results are widely standardized and traceable. Brinell uses a relatively large spherical indenter, producing an indentation that averages material properties over a small area, which is robust for calibration blocks. Rockwell uses a quick, direct-readout method with a diamond cone or ball indenter and multiple loads, delivering results efficiently with repeatable indentations.

Shore A hardness is designed for soft polymers and elastomers, not rigid metals. Mohs hardness is a qualitative mineral scale and not suitable for precise metrology on metal standards. Vickers hardness is a valid metal-scale test, but for rigid measures, Brinell or Rockwell are the conventional, specified methods due to their standardization, practicality, and traceability in calibration contexts.