Abstract
This paper presents the result of comparison of hardness, where the accurate Rockwell and Rockwell superficial hardness testing machines, their quarter load hardness testing machines (1st report) and the standardized hardness blocks of five levels are applied. The first comparison is made between the first two machines and the sub-standard hardness testing machine (National Research Laboratory of Metrology type) to confirm total accuracy of the former ones, the differences are -0.4-0 in HRB and -0.3-0 in HR 30 T. In the second comparison between HRB·FIR 30 T and their quarter load hardness HRBQ·HR 30 TQ, the differences are -0.2-0 (HRB 100-50), -0.9 (HRB 30) between HRBQ and HRB, and -0.1-0.2 (HR 30 T 80-32) betwen HR 30 TQ and HR 30 T. These values are small enough to verify the utility of HRBQ and HR 30 TQ. Moreover, the utility of the other quarter load hardness scales is presumed. The errors of geometric similarity of indentations, that is, the differences between d2Q : d2 (the ratios of diameters of HRBQ·HR 30 TQ indentations to those of HRB·HR 30 T indentations, respectively) and 1 : 2 (the ratio of the sizes of the respective indenters) are lower than 1%. The errors of similarity in hardness, that is, the differences between hbQ : hb (the ratios of the depths of indentations which are calculated with respective hardness numbers) and 1 : 2 are lower than 1%.
