In the present investigation, the effect of the tool rotational speed as well as the conical angle on
the quality of friction stir drilled holes in AA7075 aluminum alloy sheets was studied. The diameters of the
developed holes, the bushing height and the bushing wall-thickness were measured to evaluate the effect of the
aforementioned parameters on the dimensional accuracy of the holes and bushing. The holes were friction stir
drilled using CNC machine at several tool rotational speeds of 3250, 3550 and 3900 rpm as well as using drill
tools having different conical angles of 38o, 42o and 58o. The analysis of variance (ANOVA) was used to
determine the level of significance of the investigated friction stir drilling process parameters on the
aforementioned hole characteristics. The regression analysis models were developed to predict the hole
diameters and bushing dimensions. The results revealed that the maximum hole diameter (15.35 mm), bushing
height (7.92 mm) and wall-thickness (1.62 mm) were noticed for holes friction stir drilled using tool rotational
speed and conical angle of 3250 rpm and 58o, respectively. The conical angle has higher significant effect on
hole diameter and the bushing wall-thickness than the spindle speed. While, for bushing height, the tool spindle
speed exhibited higher significant effect than the tool conical angle.