In given article it is shown, that on course of assembly process, except for other parameters, the geometry of working surfaces of details influences too. To define the optimum form of edges compared three various variants. As a result of the analysis of forces of the friction arising between contacting details, have come to conclusion, that the optimum form is the edges with radius form. Also in article is shown, that from standard parameters of a roughness only two influence on accuracy of performance of assembly process, namely: arithmetical mean deviation of the profile (Ra) and mean spacing of the profile irregularities (Sm).