This work presents experimental measurement for determination of dependence of the prestressing force on the prestressing moment in order to determine the friction factor occuring on the sides of the threads while tightening the bolted joints, i.e. connection of the rod with the turnbuckle. In the introductory part of this work, the bolted joints, the friction factor and momentum of force are briefly described. After the introduction, follows the description of elements and all of the tools used in the experimental testing. In the experimental part of the work, 4 series of tightening were done, with the first tightening being done with a dry thread and the rest with a lubricated thread. The results of experiements are shown in the spreadsheet and in the graphs. The comparsion was done after taking the average results from the data.