Influence of pilot hole on cutting force during threading with wireless holder system

This paper examines the machining accuracy when simultaneously machining pilot holes and threads, and the machining accuracy when machining threads after pilot hole drilling. To verify them, cutting forces were measured in the tool rotation coordinate system using a wireless holder. To examine the influence of the machining area of the tool bottom edge machining the pilot hole, three patterns of pilot hole diameters (phi 0 mm, 7.0 mm, and 8.5 mm) were used. The results showed that when the pilot hole diameter is phi 0 mm, the cutting force in the plane direction does not increase significantly compared to the case with a pilot hole due to the offset effect of the cutting forces generated by the facing cutting edges when machining the bottom edge. Therefore, if chip entrapment can be prevented, it is highly possible to omit the pilot hole, improve machining efficiency, and maintain machining accuracy. It was also found that tool vibration could be reduced. However, when the pilot hole diameter is Phi 0, the load in the tool axis direction increases. Therefore, it was also found that machine rigidity and tool life must be considered due to the increased load during machining. These results are summarized in this paper.