<p>Machining defects are directly influenced by tool wear. However, the combined effect of various tool wear areas restrains the identification of the defect generation mechanism. Therefore, it is worthwhile to identify the effect of different tool wear areas on the generation and distribution of drilling defects. Here, the relationship between specific worn areas and drilling defects was discussed and the quantifiable comparison was studied in detail. Drilling tools with three different wear areas, namely, a chisel edge, a main cutting edge, and an outer corner, were customized. The characteristic evolution rules for the roughness surface ratio, porosity, burr area ratio, and delamination factor were analyzed for different tool wear areas. It was found that the drilling defects were different when induced by specified tool wear areas. The chisel edge wear exhibited the fewest burrs (1.31%) and the fewest delamination (<i>Z</i>₁: 1.06) at the hole exit, with regular grooves presented on the drilled surface. For the wear on the main cutting edge, numerous pits appeared, with the highest proportion of burrs (4.66%) at the hole exit and the most obvious delamination (<i>Z</i>₁: 1.03) at the middle zone of CFRP holes. The outer corner wear presented more significant pits (7.72%) and the most serious delamination (<i>Z</i>₁: 1.97) at the exit of CFRP holes. By analyzing the contribution percentage of different wear areas to different defects, it was determined that the wear for the main cutting edge had the highest contribution percentage (51.48%) to burrs and rough surface area percentage (39.31%). For the surface porosity and delamination, the outer corner wear possessed the predominant contribution percentage (60.68% and 44.62%, respectively). This work will provide a comprehensive understanding of the drilling defects generating mechanism induced by various worn tool areas.</p>