The paper is devoted to the topical issue of the formation of a variation method for calculating the accuracy of metal cutting systems. The current state of the basic variation method for calculating the geometric accuracy of metal cutting machines is determined. A transition from considering the geometric accuracy of only the metal cutting machine to considering the accuracy of the metal cutting system is made, which includes the metal cutting tool. The proposed directions for the development of the method are recommended to be divided into groups according to the criterion of linearized and non-linear formulation when building accuracy balances. The solution of the problem posed in the paper serves as a methodological basis for work on normalization and compensation of geometrical errors of machine tools, including the creation of the foundations of standards for the accuracy of metal-cutting machines and tools. This work is useful for scientists engaged in the study of the geometric accuracy of processing on metal-cutting machines, as well as the normalization and compensation of the geometric errors of machines.