Do you ever wonder how far to space indents when performing Rockwell hardness tests?
Indent spacing is a common concern during specimen testing or coupon block verification. Your results can be adversely influenced by spacing indents too close to one another or to the edge of the material. The accepted criteria are that the distance from the center of any indentation should be at least three times the diameter of the indentation. The distance from material edge to the center of any indentation should be at least two and one-half times the diameter of the indentation. The purpose for these distances is to ensure that any new indentation is not influenced by work hardening of the edge of the material or material around a previous indentation. Also, the edge distance requirement ensures that the indentation’s area of contact permits proper support.