A suitable geometrical model for the verification of Knoop indenters with Gal-Indent optical system

ISO 4545-2 and 4545-3 of Knoop hardness tests require the geometrical verification of the indenter. INRiM hardness laboratory developed a specific measuring system, commercialized by Galileo-LTF as Gal-Indent optical system, which is used for the verification of Vickers indenters. This system is able to measure the vertex angles of the indenter between two opposite faces, and the four quadrilateral base angles. Using such quantities as inputs of a suitable geometrical model, the geometry of Knoop indenters can be verified. This work deals with the description of the system and the geometrical model.