Ideas to world-wide Unified Scales Rockwell Hardness Test with Conical Indenter. Results of the round robin test, differences between the laboratories

The aim of the round robin test under discussion is a world-wide unification for hardness scales Rockwell using diamond indenter (HRC, HRA, HRD, HR15N, HR30N and HR45N). This aim is of high industrial need. For this purpose it is essential that the differences of the calibration values of the reference material world-wide are within small tolerances. To achieve that a cooperative work of National Metrological Laboratories is necessary. But, before, it is indispensable to define a common procedure of the whole indentation cycle because the definitions in the standards are not sufficient and must be defined with higher precision. Some parameters of Rockwell hardness test have a very significant influence on measurement results, e.g. duration of the test forces, indentation velocity and indenter geometry. The round robin test should show, which of the standardizing machine of the participating laboratories can reach the aim of small differences influenced by the standardizing machine and by the indenter used and give hints how to reach world- Wide unification of the scales.