Abstract: Improvement of the quality of mechanical parts and products is one of the high-priority tasks. This task is achieved by increasing accuracy, automation of control and implementation of a single concept of part accuracy assurance at all stages of life cycle. The tool to solve this task is a universal algorithm created by the authors to construct and visualise a geometrical model of a real part. The scientific novelty of the resaerch is caused by the fact that the authors take into account information capacity of elements, coordinate planes and axes and materialized sets of parts bases. The practical important of the algorithm is proved by the results of using it as a method of regulating dimensional and geometrical accuracy of a mechanical part. In the process of building a geometrical model, the authors have used the modular principle where a possible number of freedom degrees deprived by each element of the module is known beforehand. Geometrical model's properties, notes and recommendations are input in the form of a matrix into the data base. The geometrical model starts with the image of a generalized coordinate frame OXYZ on a one-three view contour drawing of a mechanical part. The number and image of coordinates and initial calibration accuracy of each main base are determined by the number and image of movements that haven't been spent by the base for creating a generalized coordinate system. Angular coordinate sizes and graduation errors are calculated starting from coordinate axes with the 4 and 2 information capacity and marked on projections perpendicular to turning point axes. Linear coodinate sizes and their graduation errors are calculated along relevant coordinate axes together with the reference coordinate values including zero values. The surface of elements which bases materialize coordinate systems and executive surfaces have an inclined form that is visualized on the model as the main wavy lines tangent to the elements. The main feature of this approach which also reflects the novelty thereof is that it allows to objectively evaluate all necessay geometrical characteristics of a mechanical part based on the principle of unity of bases. The algorithm offered by the authors may form the basis for developing the automated quality management system in the processes of mechanical part design and production.