# Cutting Performance and Wear/Damage Characteristics of PCBN Tool in Hard Milling
## 3 Experimental Analysis  
### Milling Force  
Thermal load and mechanics loads affect tool life and machined surface integrity. Because of the characteristics of milling, it is difficult to measure the cutting heat, but the cutting force can be easily obtained. Therefore, the cutting force measured by experiment was selected to evaluate the cutting performance of the tool.  
(1) Cutting Speed (Test 1)  
The influence of cutting speed on the cutting force of the two kinds of cutting tools is shown in Figure 3.  
Figure 3: \(Cont.\)  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Test** & **Cutting Speed** & **Feed per Tooth** & **Axial Depth of** & **Radial Depth of** \\
**(m/min)** & **(mm/tooth)** & **Cut (mm)** & **Cut (mm)** \\ \hline
1 & 50, 150, 250, 350 & 0.05 & 0.05 & 0.3 \\
2 & 250 & 0.1, 0.15, 0.2, 0.25 & 0.05 & 0.3 \\
3 & 250 & 0.05 & 0.1, 0.15, 0.20, 0.25 & 0.3 \\
4 & 300 & 0.15 & 0.3 & 0.3 \\
5 & 376 & 0.1 & 0.3 & 0.3 \\
6 & 250, 314, 376, 440, 500 & 0.25 & 0.3 & 0.3 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Machining parameters.  
When the cutting speed exceeded 150 m/min, the cutting force increased rapidly for the cemented carbide tool (BNM-200). The main reason was that, when the cutting speed was high, the cutting temperature rose rapidly. The cemented carbide tool cannot withstand high temperature, which results in a large degree of wear and even edge chipping. With the increase of cutting speed, the cutting performance of PCBN tools (DCC500) can be better reflected. The cutting force in three directions decreased gradually with the increase of cutting speed. The reason was that, with the increase of cutting speed, the temperature of the cutter-chip contact area increased, which made the workpiece material produce a thermal softening effect.  
(2) Feed per Tooth (Test 2)  
The influence of feed per tooth on the cutting force of the two kinds of cutting tools is shown in Figure 4. The cutting force of the two cutters increased with the increase of feed per tooth. The reason was that the metal removal rate increased with the increase of feed per tooth. The cutting force of the PCBN tool (DCC500) was less than that of the carbide tool (BNM-200).  
Figure 4: The effect of milling speed on milling forces: (**a**) Fx; (**b**) Fy; (**c**) Fz.  
Figure 3: The effect of milling speed on milling forces: (**a**) Fx; (**b**) Fy; (**c**) Fz.  
(3) Axial Depth of Cut (Test 3)  
The influence of axial depth of cut on the cutting force of the two kinds of cutting tools is shown in Figure 5. The cutting force of the two cutters increased with the increase of axial depth of cut. The reason was that the metal removal rate increased with the increase of axial depth of cut. Compared with cemented carbide cutting tools (BNM-200), PCBN cutting tools (DCC500) had a gentle trend of change in cutting force and higher stability.  
In total, the cutting force of the PCBN tool was less than that of the cemented carbide tool under the same cutting conditions. The reason was that the friction coefficient between the cemented carbide tool and the workpiece was larger than that of the PCBN tool [19; 20].