The Rockwell scale measures a material’s resistance to indentation as a measure of hardness. The Rockwell test gauges how deeply an indenter penetrates a material under a heavy load (major load) in comparison to how deeply a preload penetrates (minor load). Different scales that employ various loads or indenters are identified by a single letter. The outcome is a dimensionless number denoted by the letters HRA, HRB, HRC, etc., where the last letter stands for the appropriate Rockwell scale. A minor load and a major load must be applied to a material in order to determine its Rockwell hardness.

 The zero position is established by the minor load. The minor load is kept constant while the big load is applied and removed. A dial that measures the depth of penetration relative to the zero datum uses a harder material to get a lower reading. In other words, the hardness and penetration depth are inversely related. The main benefit of using Rockwell hardness is avoiding the time-consuming calculations required by other hardness assessment systems by simply displaying hardness values.

The following Rockwell Scales are used in Universal Hardness Tester for Vickers / Knoop, Rockwell and Brinell: HRA, HRB, HRC, HRD, HRE, HRF, HRG, HRH, HRK, HRL, HRM, HRP, HRR, HRS, HRV.

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