MACHINING SCIENCE AND TECHNOLOGY, vol.28, no.1, pp.1-27, 2024 (SCI-Expanded)
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.