# The Impact of Drilling Parameters on Drilling Temperature in High-Strength Steel Thin-Walled Parts
## 4 Effect of Drilling Dosage on the Temperature During Thin-Wall Drilling  
The effect of cutting speed on drilling temperature was investigated by varying the spindle speed (\(n\) = 500 r/min, \(n\) = 750 r/min, \(n\) = 1000 r/min, \(n\) = 1250 r/min, \(n\) = 1500 r/min) at a feed rate of \(f\) = 0.025 mm/r. The temperature field on the bottom surface of the workpiece at different drilling speeds with the drill at four different characteristic positions A\({}^{\prime}\), C\({}^{\prime}\), F\({}_{\rm max}\) and T\({}_{\rm max}\) in Figures 3 and 4 is shown in Figure 7.  
As can be seen from Figure 7, the change in the temperature field on the bottom surface of the workpiece during the drilling process is generally consistent with the previous analysis. From the location of the maximum axial force, at \(v_{\rm c}\leq 18.84\) m/min (\(n\leq 750\) r/min), the maximum cutting force point F\({}_{\rm max}\) ahead of the top edge of the drill bit is drilling into the bottom surface of the workpiece at the point C\({}^{\prime}\). This is mainly because the cutting speed is small, the cutting temperature is low, the workpiece cutting zone softening degree is small, and the drilling edge of the yielding deformation of the thickness of the flange is small; thus, the maximum cutting force occurs entirely along the main cutting edge. The maximum cutting force occurs when the main cutting edge is completely drilled into the workpiece, and the top edge is not yet drilled out of the bottom surface. This can also be seen from the distribution of the temperature field when the axial force reaches the maximum point F\({}_{\rm max}\), as shown in Figure 7. When \(v_{\rm c}\leq 18.84\) m/min (\(n\leq 750\) r/min), the high-temperature region is small, reflecting the extrusion friction region of the top edge; while \(v_{\rm c}\geq 25.12\) m/min (\(n\geq 1000\) r/min), the high-temperature region is large, including the extrusion friction of the top edge and the main cutting edge on the drill cap. From the characteristics of temperature field distribution, when the maximum temperature is reached on the bottom surface of the workpiece, as shown in Figure 7, the distribution of the maximum temperature is relatively flat at \(v_{\rm c}\geq 18.84\) m/min (\(n\geq 750\) r/min), and the distribution area is close to the diameter of the drilled hole. From the diffusion of the temperature field on the bottom surface of the workpiece, the lower the drilling speed, the larger the heat diffusion area on the bottom surface of the workpiece. The higher the drilling speed, the smaller the area of the heat diffusion zone in the drilling process; the width of the distribution of the various temperature bands becomes significantly smaller, and the temperature gradient increases. On the one hand, the low drilling speed produces less heat; on the other hand, the low drilling speed makes the heat diffusion time longer. Thus, the heat diffusion area on the bottom surface of the workpiece becomes larger. From the temperature field diagram in Figure 7, the influence of drilling speed on the maximum temperature when the drill is in the four characteristic positions of A\({}^{\prime}\), C\({}^{\prime}\), F\({}_{\rm max}\) and T\({}_{\rm max}\) is shown in Figure 8. It can be seen that the maximum temperature of the drilling centre on the bottom surface of the workpiece when the drill is in the four characteristic positions of A\({}^{\prime}\), C\({}^{\prime}\), F\({}_{\rm max}\) and T\({}_{\rm max}\) increases with the increase in drilling speed. Among these positions, the maximum temperature of the bottom surface of the workpiece increases with the increase in cutting speed. This occurs to a smaller extent at the position of A\({}^{\prime}\) when the top edge of the drill has not yet drilled into the surface of the workpiece.