Machining accuracy is the degree to which the actual size, shape and position of the surface of the machined parts conform to the ideal geometric parameters required by the drawings. The ideal geometric parameter, for the size, is the average size; for the surface geometry, it is the absolute circle, cylinder, plane, cone and straight line, etc.; for the mutual position between the surfaces, it is the absolute parallel , vertical, coaxial, symmetrical, etc. The deviation of the actual geometric parameters of the part from the ideal geometric parameters is called the machining error.
