The purpose of this standard is to unify the technical conditions for examining the geometric precision of machine tools operating in vacuum or in finished conditions, by means of geometric verifications and practical tests. A machine tool is a machine that is not portable during work, powered by an external source of energy and that allows the machining of metal, wood, etc., by removing material or by deformation. This standard is applicable in principle only to machines that work by removing material, not contemplating the particularities of machines that work by deformation, nor those that work with wood or other non-metallic materials. Geometric verifications are understood as those corresponding to the dimensions, shapes and positions of the different parts of the machine, as well as their respective movements. They include all verification operations that affect said bodies, such as: surface flatness, coincidence and insertion of axes, parallelism and perpendicularity between straight lines and flat surfaces, etc. However, they only concern the dimensions, shapes, positions and relative displacements that may influence the working precision of the machine. Practical tests consist of the execution of standard parts, with specific dimensions and tolerances, related to fundamental operations for which the machine has been designed. After general considerations on definitions, verification processes and instruments as well as tolerances, this standard deals more broadly with control operations, practical tests, geometric verifications and some controls. specials. The verification instruments are the subject of the annex.