Abstract
The growth and falling off of the built-up edge occur frequently in the drilling opereration of aluminium alloys and the behavior of the built-up edge strongly affects the conditions of the drilled surfaces. In this study, the behavior of the built-up edge in the drill edge, quality of the drilled surfaces, etc. in the drilling of aluminium alloy 5052-F are investigated by quickly stopping the cutting operation of the twist drill, in order to examine the aluminium drilling mechanism. The results obtained are as follows. In dry drilling, the built-up edge grows remarkably, the adhering condition of the built-up edge changes continuously and the actual rake angle which participates in cutting shows a nearly constant value of about 35° on the drill edge, regardless of the change in the drill rake angle between −30° and +30° from the center to the magin, and the nose radius of the built-up edge is nearly constant at about 60 μ. When the cutting fluid is dropped in drilling, the built-up edge decreases suddenly, but, in drilling using dry ice cooling and no cutting fluid, the built-up edge shows dominant growth. This results suggests that lubrication is more effective for the control of the built-up edge than cooling. It is also shown that the drilled surface (the conical surface, particularly the cylindrical surface) is greatly affected by the built-up edge.
