## 3 Results  
The data obtained from the experiments are presented in Table 1 and Figure 5. The results of the investigation showed that drill 1 without a hole (with increasing groove helix) generated the temperature of 38.4 \({}^{\circ}\)C at the speed of 800 rpm with cooling. When the speed increased the heat production increased accordingly, but the maximum values were still acceptable (T\({}_{3000}\)max = 61.5 \({}^{\circ}\)C and T\({}_{5000}\)max = 63.8 \({}^{\circ}\)C). On the other hand, drill 2 with a hole showed that even if the interrupted drilling protocol was used, the temperatures were higher than those produced by drill 1. The maximum temperatures generated by the drill were T\({}_{5000}\)max = 75.4 \({}^{\circ}\)C, T\({}_{3000}\)max = 65.5 \({}^{\circ}\)C and at the speed of 800 rpm the drill was completely blocked inside the PUR foa  
Figure 4: An experimental setup: 1—IR camera with connection to PC 2—PUR block; 3—vertical axis of CNC machine with rotary function; 4—measured drill (cutting disc); 5—CNC machine with three axis movement; 6 and 7—PC for drill movement controlling and recording data from IR camera. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Drill Number** & **Type** & **Revolutions (rpm)** &
\begin{tabular}{c} **Maximum** \\ **Temperature (\({}^{\circ}\)C)** \\ \end{tabular} \\ \hline \multirow{3}{*}{**1**} & \multirow{3}{*}{conical} & 800 & 38.4 \\ \cline{3-4}  & & 3000 & 61.5 \\ \cline{3-4}  & & 5000 & 63.8 \\ \hline \multirow{3}{*}{**2**} & \multirow{3}{*}{conical} & 800 & \(\mathrm{N}/\mathrm{A}\) \\ \cline{3-4}  & & 3000 & 75.4 \\ \cline{3-4}  & & 5000 & 65.5 \\ \hline \multirow{3}{*}{**6**} & \multirow{3}{*}{cutting disc} & 800 & 27.4 \\ \cline{3-4}  & & 3000 & 27.3 \\ \cline{3-4}  & & 5000 & 26.5 \\ \hline \multirow{3}{*}{**7**} & \multirow{3}{*}{cutting disc} & 800 & 33.4 \\ \cline{3-4}  & & 3000 & 29.5 \\ \cline{3-4}  & & 5000 & 28.3 \\ \hline \multirow{3}{*}{**8**} & \multirow{3}{*}{cutting disc} & 800 & 33.2 \\ \cline{3-4}  & & 3000 & 29.4 \\ \cline{3-4}  & & 5000 & 28.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The maximum temperature detected on the thermocouple for conical drills and cutting discs during three revolutions. Version with cooling. Figure 5: The maximum temperature detected on the thermocouple for conical drills and cutting discs during three revolutions. Version with cooling. Drills 3 and 4, which are usually used to cut material in radial direction, had been moving 5 mm/min towards a PUR block. In this case, it was shown that this experimental setup with interrupted drilling protocol, cooling and drill speed of 3000 rpm was not suitable for making the hole in the radial direction of the PUR foam as drill #3 fractured and the experiment with drill #4 was stopped so that the drill would not break (Figure 7). For drills with cutting discs (5, 6, 7, 8) a similar experimental setup as for drills 3 and 4 was used, as shown in Figure 3. It could have been observed that the disc-drill was self-carrying cooling medium into the depth of the slot (Figure 8). Drill 5 cut the PUR foam very easily but with the vertical part, which was in this case made for radial cutting. The vertical part of this drill that is used for making the slot, did not manage to cut the PUR foam with the 5 mm/min cutting movement and 3000 rpm rotational speed. The drill 5 then bent and the experiment was stopped so as not to destroy the drill. Figure 8: On the left, cutting disc carrying cooling medium into the depth of the slot. On the right, drill 5 bent at 3000 rpm. Figure 6: The experiment with conical drill #2 was interrupted when it got blocked in the PUR foam at the speed of 800 rpm. Figure 7: On the left, fractured drill 3 and on the left drill 4. For cutting discs 6, 7, and 8 the vertical slots with 2.7 mm thickness were first milled as shown in Figure 9a (drills number 7 and 8), and then horizontal slots were made by the cutting discs (Figure 9b). The horizontal slots were made by interrupted drilling protocol and with 5 mm/min horizontal cutting speed.