The measuring error of the depression has a large influence upon the hardness which is calculated by the area of depression.
The author studied the surface indented by Brinel, Vickers and Knoop depressions using Ogoshi Surface Roughness Tester, and found that for the same metal the piling-up was almost constant regardless of the applied weight and the measuring error, i. e. the error of hardness, differs with the metal. It was also found that there was a slight piling-up in the diagonal of Vickers depression but no piling up in the major diagonal of Knoop depression.
