Rockwell hardness testing

A method for testing the hardness of metals by determining the depth of penetration of a steel ball or a diamond sphero-conical indentor. The value is read from a dial and is an arbitrary number related to the depth of penetration. For testing hard steels, a sphero-conical diamond is used with a 150 kg load, the result is read from the black scale on the dial and is prefixed with the letter C. A hardened tool steel would typically give a reading of 62Rc. For softer metals Scale B is used with a 1/16" diameter steel ball and a standard load of 100 kgs.