## 3 Experimental Results and Analysis
### Influence of Cutting Speed (Spindle Speed) on Axial Force and Deformation in Drilling
The previous analysis shows that, due to the low stiffness of the thin-walled plate of AF1410 high-strength steel, at the initial stage of the drill contacting the workpiece, the workpiece undergoes elastic convex deformation under the action of the axial force of the top edge of the drill, and the drill does not cut into the workpiece obviously, and the axial force is mainly caused by the elastic resistance of the workpiece, and the maximum axial force at this stage depends on the support force required for the drill to cut into the workpiece, and the drill only starts to cut into the workpiece when the elastic resistance is sufficient to support the drill to cut into it. When the elastic resistance force is enough to support the drill bit to drill into the workpiece, the drill bit starts to cut into the workpiece. The results in Figure 9 show that the cutting speed has little effect on the support condition of the drill bit to drill into the workpiece. The previous analysis shows that the maximum axial force occurs when the cutting speed \(v=25.1\)-\(37.7\) m/min (\(n=1000\)-\(1500\) r/min) is about to be drilled out of the bottom surface of the workpiece at the intersection point of the main and vice cutting edges, which is caused by the plastic flanging deformation that occurs underneath the cutting edge, and the thickness and width of the flanging deformation occurring underneath the drill bit is not affected by the increase of the cutting speed from 25.1 m/min to 31.4 m/min due to the increase in temperature of the material underneath the drill tip. When the cutting speed increases from 25.1 m/min to 31.4 m/min due to the increase in temperature of the material below the drill tip, the thickness and width of the flanging deformation increase, and the maximum axial force increases, but with the further increase in cutting speed to 37.7 m/min, due to the further increase in temperature, the material softens, and the maximum axial force decreases to a certain extent. Considering Figures 6 and 8, if one wants to achieve  
The previous analysis shows that at the early stage of drilling, due to the low stiffness of the workpiece, the elastic convex deformation occurs under the pressure of the top edge, the drill bit does not drill into the workpiece, the axial force grows linearly, and the moving distance of the drill bit at this stage is approximated to the amount of convex deformation of the center of the workpiece. If the time of linear growth of axial force in the early stage of drilling is \(\triangle t\), then the convex deformation \(\Delta\) (mm) is as follows:  
\[\delta=\frac{\triangle t\times n\times f}{60} \tag{2}\]  
In Equation (2), \(n\) is the spindle speed (r/min) and \(f\) is the feed (mm/r). The effect of cutting speed on the amount of convex deformation of the workpiece at the initial stage of drilling is thus calculated as shown in Figure 10.  
As seen in Figure 10, the cutting speed has little effect on the elastic convex deformation of the workpiece before the drill bit drills into the thin-walled plate at the initial stage of drilling. Since the elastic convex deformation of the workpiece before drilling in directly affects the size and shape accuracy of the hole after the workpiece elasticity is recovered, the results in Figure 10 also show that the cutting speed has little effect on the size and shape accuracy of the hole due to elastic deformation of the drilling process of the thin-walled plate of high-strength steel.