## 2 Experimental Setup  
Due to the many expensive experiments carried out, in this research, turning operations were performed without lubrication and cooling agents. During the turning of the hard steel to determine the influence of the tools on the cutting temperature, the three-factor plan of the experiment was used at five levels (Table 1). To determine the difference between the tool materials, two inserts were selected for experiments, cubic boron nitride and hard metal. As one of the hard-working materials, EN 90 MnCrV8 is known as a cold working steel. This material has a hard-wearing hardness of 55 HRC. Steel is thermally treated in such a way to ensure the mentioned hardness in the machining zone of each workpiece. The chemical composition of the selected material is shown in Table 2.  
Specifications of the tool insert are presented in Table 3. The same experimental plan was carried out for both the tool materials, as shown in Table 4.  
According to the experiment plan, testing was carried out by turning on a round workpiece. By way of preparation, workpieces with a diameter of 34 mm and a length of 500 mm were machined on the conventional lathe with a power of 10 kW. During the experiment with two types of tools, namely CBN and HM, the cutting temperatures were monitored. For the purpose of measuring the cutting temperature, a FLIR E50 (FLIR systems, Wilsonville, Oregon, US) thermal camera was used. In order to ensure the measurement of accurate cutting temperatures, the thermal camera was fixed on a tool holder (Figure 1). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Machining Parameters** & **Level 1** & **Level 2** & **Level 3** & **Level 4** & **Level 5** \\ \hline Cutting speed v\({}_{c}\) (m/min) & 80 & 90 & 120 & 160 & 180 \\ Feed f (mm/rev) & 0.045 & 0.05 & 0.1 & 0.2 & 0.25 \\ Depth of cut a (mm) & 0.07 & 0.1 & 0.22 & 0.5 & 0.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Turning conditions. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Inserts** & \begin{tabular}{c} **Rake** \\ **Angle** \\ \end{tabular} & \begin{tabular}{c} **Back** \\ **Angle** \\ \end{tabular} & \begin{tabular}{c} **Inclination** **Angle** \\ \end{tabular} & \begin{tabular}{c} **Tool Cutting Edge** \\ **Angles** \\ \end{tabular} & \
\begin{tabular}{c} **Nose** \\ **Radius** \\ \end{tabular} &
\begin{tabular}{c} **Side** \\ **Clearance** \\ \end{tabular} \\ \cline{2-9}  & \(\gamma\) (\({}^{\circ}\)) & \(\alpha\) (\({}^{\circ}\)) & \(\lambda\) (\({}^{\circ}\)) & \(\kappa\) (\({}^{\circ}\)) & \(\kappa_{1}\) (\({}^{\circ}\)) & \(r\) (mm) & (\({}^{\circ}\)) \\ \hline \multirow{2}{*}{CBN} & CNMA & \multirow{2}{*}{\(-\)6} & \multirow{2}{*}{6} & \multirow{2}{*}{\(-\)6} & \multirow{2}{*}{91} & \multirow{2}{*}{5} & \multirow{2}{*}{0.4} & \multirow{2}{*}{0} \\  & 120404 & & & & & & \\ \hline \multirow{2}{*}{HM} & CNMA & \multirow{2}{*}{\(-\)6} & \multirow{2}{*}{6} & \multirow{2}{*}{6} & \multirow{2}{*}{91} & \multirow{2}{*}{5} & \multirow{2}{*}{0.4} & \multirow{2}{*}{0} \\  & 120404 & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Specifications of inserts that were used as tool material. The thermal camera was moved in the same area at the same time with the tool. The 0.95 parameters as the emission factor were adopted as the highest chip temperature. In the selected area, the thermal camera simultaneously measured the minimum, maximum, and average temperature. During the entire machining process, the cutting temperature was monitored, while the calculation was executed every 5 s.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Factor**} & \multicolumn{2}{c}{... \(\mathbf{\Theta_{1}}\)**Measured**} & \multicolumn{2}{c}{\(\mathbf{\Theta_{1}}\)**Model**} \\ \cline{2-7}
**No. ** & **v (m/min)** & **f (mm/rev)** & **a (mm)** & \begin{tabular}{c} **HM** \\ **\(\mathbf{\Theta}\)**(\({}^{\circ}\)C)** \\ \end{tabular}  & \begin{tabular}{c} **CBN** \\ **\(\mathbf{\Theta}\)**(\({}^{\circ}\)C)** \\ \end{tabular}  &