How should you select the gauge for a digital Rockwell hardness tester?

Taiwan Nakazawa Co., Ltd. answers for you: Digital Rockwell hardness testers feature functions such as Rockwell scale selection, plastic Rockwell scale selection (optional function), and hardness conversion between various hardness scales. They are suitable for hardness determination of ferrous metals, non-ferrous metals, and non-metallic materials.
The A scale is suitable for measuring metals with hardness values exceeding 67HRC, such as tungsten carbide, hard alloys, hard thin plates, and surface-hardened parts, with a measurement range of 20-85HRA. The B scale is used to measure the hardness of non-ferrous metals and their alloys, annealed steel, and other low-hardness parts, with a hardness range of 25-100HRB. The C scale is suitable for hardness testing of specimens such as carbon steel, tool steel, and alloy steel that have undergone quenching or tempering treatment, with a measurement range of 20-67HRC.