Rockwell Hardness Tester

The Rockwell hardness tester measures a material's hardness by pressing an indenter, either a diamond cone or a hardened steel ball depending on the material and scale, into the surface under a small preliminary load followed by a larger main load, and reading the hardness directly from the difference in indentation depth between the two loads. The American metallurgists Stanley P. Rockwell and Hugh M. Rockwell developed the test while working at a ball bearing manufacturer and were granted a patent for it in 1919, seeking a faster method than the existing Brinell test for checking the hardness of hardened steel bearing races on a production line. Because the Rockwell method reads hardness directly from indentation depth rather than requiring a separate microscope measurement of an indentation's diameter, it became the fastest widely used hardness test and remains standard in production quality control.