## 3 Materials and Methods  
### Laboratory Measurements  
Laboratory measurements were performed on a linear rock cutting device (Figure 2a) and a laboratory drill with a diamond drill bit (Figure 2b). A detailed description of the laboratory cutting rig can be found in previous works [11; 28]. The laboratory drill is equipped with a diamond drill bit, used in dimension stone exploration and core drilling. The cutting depth of a diamond grain (cutting element) depends on its exposure in relation to the metal matrix, whereby it is not possible to adjust the cutting depth. [PERSON] et al. [29] found that its value is approx. 100 \(\upmu\)m. In order to determine the average depth of cut and the number of diamond grains in contact with the rock sample being tested, measurements were made on the drill bit using a digital microscope. The average exposure height of diamond grains was measured at 75.5 \(\upmu\)m. A drill bit with an external diameter of 50 mm and an inner diameter of 38 mm was used. Rock samples were limestones collected from three different dimension stone quarries (Table 2). Prior to the start of the test, the bulk density of each sample was determined. During the measurement, two different measuring systems were used, depending on the applicability of the sensor:  
1. a measuring system for measuring electrical power used up by cutting or drilling applied in laboratory and field tests (Figure 2a);
2. a measuring system with a force transducer was used on the device for linear rock cutting, and a measuring system with a force and torque transducer was used on the laboratory drill (Figure 2b). Figure 2: (**a**) Electrical power measuring system; (**b**) Measuring system with a force transducer and a measuring system with a force and torque transducer; (**c**) Chainsaw tool holder and cutting tool; (**d**) Synthetic diamonds in drilling bit segment. The sensor part of the measuring system for measuring power is the measuring transducer Iskra MT540, which is connected between the power supply and the electric motor of the device in order to measure the electric active power consumed by the electric motor of the device in time (Figure 2b). The transducer converts the power into an output voltage proportional to the power. Using the proportionality constant of the measuring transducer, the electrical voltage is converted into electrical power. The transducer is connected via a data acquisition device to a computer on which the measured data are stored. During laboratory measurements, a virtual instrument was used, that is, an instrument that realizes part of its functionality through software [30]. On the front panel of the virtual instrument, it was possible to monitor the change in electrical voltage, current, power and energy in real time [31]. To calculate the cutting energy, a linear rock cutting device equipped with three component force transducer was used (Figure 2a). A three-axis force transducer using octagonal rings was used, on which strain gauges were mounted in such a way as to form three Wheatstone bridges. The sensor is attached to the support element of the cutting element of the device for linear rock cutting. Powering Wheatstone bridges and transferring and storing measured data to a computer is enabled using a data acquisition device [28]. Measuring system with force and torque transducer consists of sensors for measuring the vertical component of drilling force (thrust) and torque (torsion) of a rotary drill, LVDT for measuring the vertical displacement of the drill bit, sensors for measuring the rotation speed of the drill bit, device for data acquisition and computer (Figure 2b). The elastic sensor element for measuring thrust and torsion is a steel tube on which strain gauges are mounted and electrically connected in such a way as to form two Wheatstone bridges [32]. The elastic element is fastened between two metal plates.