## 3 Results and Discussion
### Circular Saw blade Surface Temperature  
The adverse effect of the heating of the circular saw blade in the cutting zone and, thus, the resulting temperature difference between the central hole and the edge of the circular saw blade caused increasing variability in the cutting process [31]. The author of [36] also emphasized that the temperature differences of the circular saw blade between the edge and the center hole have a fundamental effect on its rigidity. Therefore, it is necessary to measure the temperature of the circular saw blade both at the rim, in the middle of the radius, and at the center hole. This demonstrates the heating and cooling principles of the circular saw blade. For experimental measurements of the surface temperature of circular saw blades, the non-contact method was used by means of an infrared sensor Calex PUA8-CF. The temperature sensor was set to three positions relative to the center of  
Figure 7: Dependence of the circular saw blade surface temperature on the feed speed at a shaft speed of 4050 rev/min: (**a**) CSB1, (**b**) CSB2, and (**c**) CSB3. the circular saw blade, as shown in Figure 8. When changing the cutting parameters, we obtained 54 data files for each circular saw blade. From the temperature values obtained under the same cutting conditions, we calculated the arithmetic mean. 1--frequency converter (UNIFREM 400 007 M), 2--sine filter (SKY3 FSM25), 3--control panel with digital display connected to the frequency converter via the RS232C serial interface, 4--electric motor, 5--V-belt transmission, 6--frame circular saw with a shaft mounted in radial bearings, 7--saw blade with clamping flanges, 8--three positions of the Calex PUA8-CF temperature sensor, 9--laptop. Figure 9 shows the temperature change during one cutting cycle. The terms \(\Delta T_{E}\), \(\Delta T_{M}\), and \(\Delta T_{R}\) represent the maximum values of the saw blade temperature at the center hole, at the center of the radius, and at the edge after cutting process. The symbol \(\Delta t\) is defined as the time required to reach the temperature of the circular saw blade after the cut to a constant value. Figure 8: Scheme of a circular saw, including a device for measuring the cutting power and the surface temperature of the circular saw blade. Figure 9: Experimentally measured values of CSB2 surface temperatures. (Feed speed = 21 m/min, rotation speed = 4100 rev/min). Figure 10 shows the dependence of the surface temperature of the circular saw blades on the feed speed at a shaft speed of 4050 rev/min. As we can see from Figure 10, the surface temperatures of the circular saw blades CSB1 and CSB2 had values at about 21 \(\pm\) 0.5 \({}^{\circ}\)C at the sensor position of 65 mm from the shaft axis (near the flanges). These temperatures increased slightly with increasing feed speed to values of 23-24 \({}^{\circ}\)C. Based on experimental measurements, the authors of [30; 40; 41] reported similar temperature values in the range of 22-24 \({}^{\circ}\)C for the area of clamping flanges. At the position of the temperature sensor of 110 mm from the shaft axis, the surface temperatures of the discs have already increased significantly to values of 24-25 \({}^{\circ}\)C. These temperatures also changed with increasing feed speed. At the last position of the sensor closest to the heel circle of the teeth (R = 155 mm) from the shaft axis, the surface temperature of the discs  
Figure 10: Dependence of the circular saw blade surface temperature on the distance of the sensor from the saw blade axis at a shaft speed of 4100 rev/min: (a) CSB1, (b) CSB2, and (c) CSB3. reached 32-34 \({}^{\circ}\)C. The authors of [35] stated a temperature value of 33 \({}^{\circ}\)C for the area of the heel circle of teeth. This area of the circular saw blades was most affected by the change in feed speed of all three areas. The temperature gradient created at CSB2 is 41-32 \({}^{\circ}\)C, and 42.6-34 \({}^{\circ}\)C at CSB1.