## 1 Introduction  
Continuous technological advances in the aerospace and energy industries, as well as molds and dies, are resulting in the increasing use of difficult-to-cut materials for responsible machine parts [1; 2; 3; 4; 5]. This necessitates the need for methods and strategies to extend the life of cutting tools. Difficult-to-cut materials, i.e., Ti alloys, Ni-based superalloys, and hardened steels, are generally characterized by low thermal conductivity and high hardening, which makes machining at high cutting speeds significantly more difficult. These are the main reasons for the rapid wear of tools, which has a negative impact on both the cutting process and the technological surface layer [6; 7; 8; 9]. Therefore, tool wear is one of the main challenges in the precision machining of difficult-to-cut materials, especially nowadays in multi-axis machining [10; 11]. In industrial practice, the torus milling cutter is increasingly being used to machine the surfaces of geometrically complex parts. This cutter, both in its monolithic form and essentially in the form of indexable round cutting inserts, is used especially in the finishing stage, mainly because of its unique geometry [12]. The vast majority of the work concerns the torus milling cutter in terms of the mechanics of the cutting process [12; 13; 14; 15]. From the analysis of the issue to date, it appears that there is a lack of work that addresses the angular positioning of the round cutting inserts in the torus cutter body. This positioningwould aim to utilize all possible active cutting edge segments on the circle of the cutting insert in a given fixed tool axis orientation. Positioning is defined as the exact location of a given object relative to an assumed reference point or line, which is usually the origin of a given Cartesian Coordinate System. Positioning, or more precisely, precise positioning, is also widely used in many areas of mechanical engineering, especially in the era of the Industry 4.0 industrial revolution [16]. In this case, the most tangible examples of precision positioning tasks are as follows: locating the probe of a measuring instrument relative to the measurement target, determining the position of the cutter relative to the workpiece, montaging a screw in the target hole using a robot arm, etc. All examples of engineering tasks related to precise positioning described above are supported by advanced systems and technologies, including measurement systems [16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. The measurement basis for precise positioning are the latest sensor technologies for single-axis, linear, or rotational measurements. The vast majority of practical applications require positioning in a plane or in a 3D space, and one of the most frequently used ones is angular positioning. These are realized by multi-axis coordinate measurement methods, such as triangulation and multilateration, as well as measurements in Cartesian and polar systems. The work in [27] presents the results of measuring the deviation of the shaft diameter after the turning process using the LTS laser triangulation sensor. A program was developed and verified whose task is to communicate between the PLC controller in the measurement system and the software for recording data obtained from the LTS laser triangulation sensor. In this case, inspection of the manufactured product is one of the most important operations in the technological production process [28]. Based on the test results, the authors concluded that this type of sensor is suitable for measuring the deviation parameter of the diameter of the machined surface. Another important issue is to reduce the positioning error of the rotary table of a multi-axis machine tool. The angular positioning error in this case causes poor quality milling of the workpiece surface. Therefore, in [29], the authors developed a system to improve this issue, using the Laser R-Test to calibrate angular positioning and compensate for positioning errors of the numerically controlled axes of the machine tool.