What factors contribute to errors in the measurement results obtained using a Rockwell hardness tester?

Taiwan Nakazawa Co., Ltd. answers for you:
I. Human error.
(1) The technical proficiency of the operator is insufficient, and practical experience is poor; it should be used by personnel familiar with the hardness tester.
(2) If loading is too fast and the dwell time is short, the hardness of low-hardness parts will be biased high, whereas if loading is too slow and the dwell time is long, the hardness will be biased low. During operation, loading should be smooth and maintain a certain dwell time.
II. Influence of the indenter.
(1) The diamond indenter does not meet technical requirements or has wear after a period of use. If the operator cannot judge the quality of the diamond, it can be verified by a metrological testing institution.
(2) The strength and hardness of the steel ball indenter are insufficient, making it prone to deformation. After the steel ball undergoes long-term deformation due to pressure, it becomes elliptical. When the short axis is perpendicular to the part surface, the indentation is shallow and the indicated value is high; when the long axis is perpendicular to the part surface, the indentation deepens and the indicated value decreases. The tolerance for the steel ball is less than 0.002mm.