Experimental comparison of the indexable drilling with different U drills on hole quality

Abstract

U drills are estimated to account for around 53% of all drilling equipment’s market share. This study compared and contrasted the impacts of the balance angle, the U drill length/diameter ratio, and the extra coolant hole opened in the chip evacuation channel on the hole quality when drilling AA 7075-T651 material. Hole quality was investigated by deviation from diameter, deviation from circularity, deviation from cylindricality, surface roughness, forces, and torque. Three cutting speeds, three feed rates, and four distinct U drills were chosen as input parameters. The studies revealed that when the U drill’s length/diameter ratio increased, the hole quality deteriorated. The best hole quality was nonetheless achieved by the tool with the additional coolant hole. The higher balance angle resulted in improved hole quality. However, it was discovered after looking at the chips and inserts that the chatter only happened while drilling with a U drill that had an additional coolant hole. While the extra coolant hole opened to the chip evacuation channel, it affected the hole quality positively but caused chatter, which negatively affected the inserts. The reasons for these results are discussed in detail.