The measurement errors due to human factors are not studied enough, compared with the errors by a measurement instrument. In these measurement achieved by the observer, the errors due to the observer occupy the major portion of the total error. The research of this paper is concerned with the coincidence method in the eye-piece of micrometer for Vickers indentation measurement. The main cause for the error in this measurement is of a human factor. The human errors consist of the difference among the observers, days and repetitions. The purpose of this research is to decrease these errors. In the measurement the function of sight is most important, since the improvement of coincidence method decreases the errors.
A simulator used in the experiment simulates a microscope for measuring Vickers indentation. In the experiment five coincidence methods were tried by the simulator, and it was found that one of these methods makes the smallest error. In this method an observer watches the tip of the indentation corner and discriminates the existance of the tip when the tip is hidden by the edge of the white target. The observer can judge easily this hidden point, and this fact decreases the error.
The coincidence method is applied to the measurement by a practical Vickers hardness tester, and it is found that this method make a small error practically. This result shows that this coincidence method is useful and the simulator accurately simulates the actual measurement.

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It goes without saying that the material of a standard block for hardness test should not fail to be homogeneous and give the same hardness number regardless the measuring points on the surface of the block, thus the hardness number measured on the block, must always agree with the standard number, which is alotted according to the same standard, independent from time and place. It is desirable, therefore, that we may obtain the reliability of hardness number as a standard by the stadard hardness block.
A great deal of studies on the standard block have been made, which seems to lead to succeed in manufacturing the standard block to certain extent, but there is still left to be discussed in details about this problem. The author discusses on the Vickers standard block on market in this paper, from the results obtained by the research on depression, especially on the piling-up. The demestic standard blocks supplied by two makrers (H_V=200-800) are tested on depression ranging from 1 to 50kg with subsequent examination of depression by the Ogoshi Surface Roughness Tester on the surface.
The results are summarized as follows:
(1) Every block shows its homogenuity having no difference in hardness number notwithstanding the measuring points.
(2) The degree of piling-up differs according to the makers, but the aspect of piling-up has the same inclination regardless the makers, and there is the highest piling-up at H_V≈400.
(3) There is no continual relationship between the hardness number measured on each standard block and the degree of each piling-up, and the influence of error on harddness caused by the piling-up is not proportional to the hardness. It seems desirable, therefore, to toke the influence of piling-up into consideration for the standard series of hardness block.
(4) And it is necessary that a standard block manufactured shold be of those materials which have less piling or piling to the equal amount at least.
(5) We can easily obtain the general aspects of the piling-up by means of the Knoop indentator.

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