## 3 Results
### Effect of the Cutting Volume  
The fragment recovery method [22] and sand-filling method [23] were used to measure the cutting volume in the linear cutting test. The first method measures the weight of rock fragments while the second measures the cutting surface by filling it with sand. In addition, photogrammetry was used to measure the cutting volume [15; 23]. In this study, a Calibry mini (a 3D scanner from Thor3d) was used to obtain the cutting volume. This scanner has an accuracy of up to 0.07 mm and can acquire 1,000,000 data points per second. After the cutting was completed, the surface of the deformed rock was scanned to obtain a mesh of the same shape, and the cutting volume was measured using the 3D modeling software Rhino (Figure 14). Figure 15 and Table 5 show the cutting volume according to the clearance angle. The cutting volume decreases as the angle increases, regardless of the cutting depth. At a cutting depth of 3 mm, the cutting volume of the UCS 50 MPa rock sample decreased the most from 4840 mm\({}^{3}\) to 2779 mm\({}^{3}\) as the clearance angle increased from 0\({}^{\circ}\) to 15\({}^{\circ}\), and on average, it decreased by 39% (Figure 15a). At cutting depths of 6 mm and 9 mm, the volume decreased by 37% and 24%, respectively, on average (Figure 15b,c, respectively). Thus, it can be concluded that the effect of the cutting volume owing to the clearance angle decreases as the cutting depth increases. The variation in the cutting volume according to the rake angle is shown in Figure 16 and listed in Table 6. In all cases, the cutting volume decreases as the rake angle increases from 0\({}^{\circ}\) to 5\({}^{\circ}\). When the cutting depth is 3 mm, the cutting volume for UCS 40 MPa \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{
\begin{tabular}{c} UCS \\ **(MPa)** \\ \end{tabular} } & \multirow{3}{*}{\(p\) **(mm)**} & \multicolumn{3}{c}{**0**} & \multicolumn{3}{c}{**5**} & \multicolumn{3}{c}{**10**} & \multicolumn{3}{c}{**15**} \\ \cline{3-10}  & & \(\mathbf{V_{c}}\) & SE & \(\mathbf{V_{c}}\) & SE & \(\mathbf{V_{c}}\) & SE & \(\mathbf{V_{c}}\) & SE \\  & & **(mm\({}^{3}\))** & **(MJ/m\({}^{3}\))** & **(mm\({}^{3}\))** & **(MJ/m\({}^{3}\))** & **(mm\({}^{3}\))** & **(MJ/m\({}^{3}\))** & **(mm\({}^{3}\))** & **(MJ/m\({}^{3}\))** & **(MJ/m\({}^{3}\))** \\ \hline
40 & 3 & 3495 & 411.0 & 2880 & 116.2 & 2229 & 122.0 & 2267 & 97.9 \\  & 6 & 11,416 & 194.4 & 10,463 & 87.2 & 8489 & 78.6 & 6892 & 88.1 \\  & 9 & 23,400 & 208.3 & 21,082 & 72.6 & 19,180 & 55.5 & 17,788 & 47.1 \\
50 & 3 & 4840 & 322.2 & 3585 & 151.8 & 3306 & 107.2 & 2779 & 93.6 \\  & 6 & 12,124 & 201.8 & 11,580 & 119.8 & 9087 & 80.2 & 8030 & 78.7 \\  & 9 & 20,855 & 235.4 & 20,065 & 107.9 & 19,638 & 62.4 & 15,772 & 73.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Cutting volume and specific energy for various clearance angles. Figure 15: Relationship between the cutting volume and clearance angle for depths (\(p\)) of: (**a**) 3 mm, (**b**) 6 mm, and (**c**) 9 mm. decreases by 23% from 2726 mm\({}^{3}\) to 2102 mm\({}^{3}\). In the case of the 50 MPa UCS, the volume decrease was 12%, from 2574 mm\({}^{3}\) to 2254 mm\({}^{3}\) (Figure 16a). When the cutting depth increases to 9 mm, the reduction rate of the cutting volume decreases to an average of 2% (Figure 16c). Subsequently, as the rake angle increased, the cutting volume also increased, although the amount of change was less than that of the clearance angle. To summarize the effect on the cutting volume according to the shape of cutting tool, the cutting volume decreased with increasing clearance angle, the rake angle caused a slight decrease when increasing from 0\({}^{\circ}\) to 5\({}^{\circ}\), and subsequent increases in angle increased the volume. This phenomenon is similar to that of the cutting force, and the cutting force and cutting volume are observed to be proportional.