HARDNESS TESTERS CALIBRATION PRACTICE

In the framework of the standardization and laboratory activities concerning the calibration of hardness testers, in particular for indirect verification there are some questions to be answered to decide an efficient metrological confirmation strategy: a) how many points on each scale shall be checked? b) How many levels of the indentation scale shall be checked? c) How many levels of forces shall be checked? d) Is the correlation between indirect results and direct results strong enough to allow a partial check of the hardness scales of the tester? A number of tests have been made and the results have been statistically elaborated to give an answer to these questions.