In this master thesis we deal with a design of a machine for assembling part in the automotive case parts. The machine must include leak testing for 100 % quality control of the assembly products. The objective of the thesis was to design a new concept of the part which will affect on the final cost of the machine. With final element method an assembling process was analysed. The optimum concept was choosen on the basis of the theoretical calculations and experimental testing of the assembly process, for which specimens were designed in order to measure the aseembly force during the formation of a press-fit joint. By combining experimental results with computer analyses it was determined the size of the friction coefficient between the assembly parts. At the end of masters thesis a comparison was made between the theoretical calculations and the results obtained from the finite element analysis.