## 1 Introduction  
Currently, only minor attention is paid to the given issue; thus, few papers have been published in this field. Most of the friction coefficient research focuses on ball and trapezoidal screws, which are used in machine tool drives. The findings have led authors to design a measuring stand for testing bolted joints, where the primary monitored parameter is the coefficient of friction between the threads. Bolted joints are a type of dismountable joint, designed to connect diverse components. From a technical point of view, their function is based on threaded coupling. Threads are referred to as functional elements, and they are standardized to a high degree. The current situation and level of technology in the mechanical coupling of components with thread fasteners are characterized as follows:  
* The prevailing results are generally underestimated, based on the fact that the screws and matrices are widely used and, compared to other structural elements, they are the cheapest available. * Double, even triple, dimensioning, which represents the weakest point of current screwing technology. On the one hand, the structural designer is frightened of bearing potential responsibility for a possible accident, and on the other hand, there is the issue of mastering the theory and practice of screwing. * Economic pressure to build light structures to achieve material savings [1]. The causes of failures in screw connections have become a subject of interest in many companies and relevant workplaces. The well-known SFK company created a hierarchy of failure causes, showing that the highest number of failures occur in assembly. This is a logical outcome of imprecise tightening. Bolted joint design includes designing materials and strength dimensioning. At the same time, requirements related to operational load must be taken into consideration. A bolted joint functions as required only if all of the mechanical properties of the individual elements are preserved, along with the degree of precision of the defined tolerated dimensions. In practice, bolted joints are subjected to load tests according to specified calculations. These tests verify the efficiency, different deformations, thread strength, etc., of bolted joints. All inevitable forces are generated when the respective screw or bolt nut is tightened with the predefined torque. Apart from the force acting in the direction of the screw axis, bolted joints induce other forces perpendicular to their axis, which are caused by friction forces. These forces especially occur in abutting areas of the connected parts. Friction force must act adequately to prevent a shift in the connected parts and consequent shear stress on the screw [2]. From the point of view of modern design engineering, assessment of the carrying capacity, the service life, and the fulfillment of the functional requirements of bolted joints is significantly influenced by the correct definition of axial force \(F_{0}\) when a screw or a bolt nut is tightened, as well as by practical procedures necessary for their achievement. If the force is extremely low in comparison to the tension tolerated in the screw core, the maximum technical parameters of the structure cannot be achieved. In case of high values, when the superposition of the force, along with the effects of other forces, reach characteristic stress in the thread core due to operational stress, the bolted joint is released or the threads are cut, which represents an unacceptable condition (tightness is insufficient, abutment joints are released, etc.). Therefore, close attention has been paid to the experimental processes, assuring the pre-stress of screws as required.