What precautions should be taken when inspecting the standard block of a digital Rockwell hardness tester?

Taiwan Nakazawa answers for you: Digital Rockwell hardness testers feature functions such as Rockwell scale selection, plastic Rockwell scale selection, and hardness conversion between various scales. Among these, the test block is a simple comparison method to check the accuracy of your hardness tester. Before performing a test block inspection with a digital Rockwell hardness tester, always pay attention to the following matters:
1. Do not use a test block where old indentations have been ground away, because it cannot be certain whether the newly processed surface has the same hardness value as the original one.
2. If the digital Rockwell hardness tester is used across the entire given scale range, the high, medium, and low ranges of the scale should be checked. If only one or two ranges are used, test blocks with hardness values above and below those specific ranges can be selected.
3. The test block should be tested on a single side only; do not test on both sides. Using the bottom or side surfaces will not yield correct hardness values.
4. Use test blocks that are in good condition. Do not use a test block where the distance between indentations is less than at least 2.5 times the indentation diameter.