Indentation and edge distance Rockwell and Brinell
The relevant standards for each of the different test methods specify minimum distances between the test points (indentations) as well as to the specimen edge. The reason for these minimum distances is to avoid distortion of the hardness testing results, which could result from the deformation of the material structure.
The illustrations below show the minimum distances for the Rockwell (acc. ISO 6508), Brinell (acc. ISO 6506), Vickers (acc. ISO 6507) and Knoop (acc. ISO 4545) methods.