In the final thesis, we focused on improving the shaft and leverage assembly, which is exposed to alternating load torque and static load axial force. We have limited space to fit this, assembly in. There are also given requirements for accuracy of position and sealing between shaft and flange. The assembly must be of good quality, as there are environmental influences such as: corrosive medium, vibrations up to 50 g, temperature differences of surroundings between –40 and 120 °C and heat fluxes between the shaft heated to 700 °C and the lever at ambient temperature. We mostly focused key impacts on coaxiality. We investigated axial runout and circular runout after welding shaft and lever in to the assembly. When we are not welding in a purpose-built preparation. The most suitable designs were made and tested experimentally in number of ways. In conclusion we found out that a large spread occurs between measurements of the same samples. That is a consequence of the unrepeatability of manual welding and the quality of welder.