Correction of squareness measurements of Vickers indenters due to the tilt of the pyramid axis

In Vickers hardness measurements, ISO 6507-2 and 6507-3 Standards require to verify that the quadrilateral of the pyramid indenter base has angles of 90° ± 0.2°. Such measurement is usually performed through optical measuring systems, which, rotating the diamond indenter, allows to evaluate the angles between two consecutive faces with high accuracy. These angles correspond to the angles of the quadrilateral base when the axis of the pyramid is perfectly perpendicular to the seating surface. Nevertheless, when the pyramid axis is tilted, the angles between two consecutive faces are different from the corresponding angles on the quadrilateral base, thus a correction is required. In this work, a method to correct squareness measurements, based on a geometrical model, is presented.