## 3 Experimental Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \(n\) & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** \\ \hline A & 2.121 & 1.732 & 1.500 & 1.342 & 1.225 & 1.134 & 1.061 & 1.800 & 0.949 \\ A\({}_{2}\) & 1.880 & 1.023 & 0.729 & 0.577 & 0.483 & 0.419 & 0.373 & 0.337 & 0.308 \\ A\({}_{3}\) & 2.659 & 1.954 & 1.628 & 1.427 & 1.287 & 1.182 & 1.099 & 1.032 & 0.975 \\ A\({}_{4}\) & 1.880 & 1.190 & 0.800 & 0.690 & 0.550 & 0.510 & 0.430 & 0.410 & 0.360 \\ B\({}_{3}\) & 0 & 0 & 0 & 0 & 0.030 & 0.118 & 0.185 & 0.239 & 0.284 \\ B\({}_{4}\) & 3.267 & 2.568 & 2.266 & 2.089 & 1.970 & 1.882 & 1.815 & 1.761 & 1.716 \\ B\({}_{5}\) & 0 & 0 & 0 & 0 & 0.029 & 0.113 & 0.179 & 0.232 & 0.276 \\ B\({}_{6}\) & 2.606 & 2.276 & 2.088 & 1.964 & 1.874 & 1.806 & 1.751 & 1.707 & 1.669 \\ D\({}_{1}\) & 0 & 0 & 0 & 0 & 0 & 0.204 & 0.388 & 0.547 & 0.687 \\ D\({}_{2}\) & 3.686 & 4.358 & 4.698 & 4.918 & 5.078 & 5.204 & 5.306 & 5.393 & 5.469 \\ D\({}_{3}\) & 0 & 0 & 0 & 0 & 0 & 0.076 & 0.136 & 0.184 & 0.223 \\ D\({}_{4}\) & 3.267 & 2.574 & 2.282 & 2.104 & 2.004 & 1.924 & 1.864 & 1.816 & 1.777 \\ C\({}_{4}\) & 0.798 & 0.886 & 0.921 & 0.940 & 0.952 & 0.959 & 0.965 & 0.969 & 0.973 \\ d\({}_{2}\) & 1.128 & 1.693 & 2.059 & 2.326 & 2.534 & 2.704 & 2.847 & 2.970 & 3.078 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Conversion coefficients for calculation of UCL, LCL in CC (_n_ = 10 in ISO 8258). Statistical characteristics at the selected confidence level were calculated for the reliability of the evaluated variables and the conclusions' accuracy. For engineering tasks, it is recommended in the standard STN ISO 8258 The control diagrams assume a theoretical probability of \(p=99.73\) % and  
Figure 8: Histograms of measured parameters, (**a**) process revolutions, (**b**) pressure force, (**c**) vibration signal of acceleration. Figure 7: Time courses of measured parameters, (**a**) revolutions, (**b**) pressure force, (**c**) vibration signal of acceleration. uncertainty of \(\alpha~{}=~{}0.27\%\). As exceeding regulatory limits is considered an exceptional phenomenon in terms of probability, the process must be intervened immediately in the event of its occurrence. Subsequently, control charts were designed and constructed according to a simple algorithm shown in Figure 9.  
The experimental drilling work aimed to obtain data on the permissible variability and dynamics of possible changes in revolutions and pressure force in interaction with the drilling tool's vibrations. Control charts were applied to the measured operating mode with the speed of revolutions \(n=800\) (rpm) and pressure force F\(=8000\) (N). The experiment's duration was \(T=55\) (s), with 220 values recorded at regular intervals (4 values per second). The drilled rock was andesite. In the calculations and construction of control charts (CC) by measuring for the variables of \begin{table}
\begin{tabular}{l r} \hline \hline
**Characteristics** & **Value** \\ \hline Mean & 744 \\ Standard Error & 4.0 \\ Median & 751 \\ Mode & 811 \\ Standard Deviation & 58 \\ Sample Variance & 3359 \\ Kurtosis & \(-1.00\) \\ Skewness & 0.00 \\ Range & 205 \\ Minimum & 648 \\ Maximum & 853 \\ Sum & 163,688 \\ Count & 220 \\ Largest (1) & 853 \\ Smallest (1) & 648 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Statistical characteristics of revolutions’ speed. \begin{table}
\begin{tabular}{l r} \hline \hline
**Characteristics** & **Value** \\ \hline Mean & 7547 \\ Standard Error & 32 \\ Median & 7483 \\ Mode & 7459 \\ Standard Deviation & 471 \\ Sample Variance & 221,970 \\ Kurtosis & 1 \\ Skewness & 0 \\ Range & 2666 \\ Minimum & 6666 \\ Maximum & 8732 \\ Sum & 1,660,295 \\ Count & 220 \\ Largest (1) & 8732 \\ Smallest (1) & 6066 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Statistical characteristics of measured pressure force.