Abstract

In manufacturing, the progressive deterioration of hole quality during drilling particularly in aluminum alloys such as Al-5083 is a critical concern due to its direct impact on assembly accuracy and tolerance control. This study investigates how machining time influences drilled hole geometry, while establishing the role of chip behavior as an in-process indicator of drilling stability. A total of 52 consecutive holes were drilled using a High-Speed Steel (HSS) tool, and three geometric quality measures such as circularity, cylindricity, and conicity were evaluated for each hole. In addition, the interrelationship among these geometric errors was examined. Throughout the drilling sequence, chip morphology exhibited a clear transition from ideal, continuous ribbons in the initial stage to unstable “Transition chips” as machining progressed. Although the geometric errors did not show strong trends in isolation, the occurrence of transition chips consistently coincided with the largest deviations in hole geometry. Notably, these unstable chips were responsible for approximately 75% of holes that failed to meet industrial tolerance limits. The findings highlight that chip morphology serves as a practical real-time indicator of drilling stability and final hole quality, offering a valuable complement to traditional post-process geometric inspection.

Keywords:

Drilling, Machining time, Hole Accuracy, Chip Morphology, Tool wear