8. Checking machines and hardness blocks

For hardness measured by indentation, there are no fixed natural points on which to establish an absolute hardness scale. It is necessary to take into account all the factors that can influence the value given by a machine. This leads to specific recommendations for each test method, and to specific checks for each type of machine (standards NF EN ISO 6506-2, NF EN ISO 6507-2, NF EN ISO 6508-2, NF EN ISO 14577-2 respectively for Brinell, Rockwell, Vickers and penetration testing machines). These standards enable us to obtain mutually comparable measurements with equipment tested in this way.

Hardness testing machines are calibrated either by direct methods or by indirect methods using reference blocks.

With the first methods, the various components of the measurement chain need to be calibrated successively: measurement of applied force,...