The determination of the Rockwell hardness of a material involves the application of a minor load followed by a major load. The minor load establishes the zero position. The major load is applied, then removed while still maintaining the minor load. The depth of penetration from the zero datum is measured from a dial, on which a harder material gives a lower measure. That is, the penetration depth and hardness are inversely proportional. The chief advantage of Rockwell hardness is its ability to display hardness values directly, thus obviating tedious calculations involved in other hardness measurement techniques.
For Standard Rockwell Hardness Test Blocks – ASTM E-18 and ISO 6508 Major Load varies all the way from 60KG for HRA, HRF, HRH, HRL, & HRR scales to 150KG for HRC, HRG, HRK, & HRP scales.
For Superficial Rockwell Hardness Test Blocks – ASTM E-18 and ISO 6508 Major Load varies from 15KG at Hardness Scale HR15N to 45KG at Hardness Scale HR45Y.