Abstract
As the formation and breakdown of the built-up edge occurs repeatedly in drilling aluminum alloys, the behavior of the built-up edge and the appearance of the drilled surface in aluminum wrought alloys, 1100-F, 2024-T4, 5052-F and 6061-T6, have been studied by quick-stopping of cutting operation of a twist drill for the purpose to examine the aluminum drilling mechanism. The results obtained are as follows.:
In dry drilling, the built-up edge is generally formed and the adhering condition of the built-up edge changes continuously as the drill rakc angle changes from -30° to +30° from the center to the margin. But, the effective rake angle of cutting is nearly constant (about 35°), and the nose radius of the built-up edge is also nearly constant (about 60μ). In the case of 5052-F, the built-up edge is formed on the whole drill edge. For 2024-T4 and 6061-T6, the built-up edge is formed near the center and only a little near the margin of the drill edge. For 1100-F, the built-up edge is formed very little. It seems that the formation of the built-up edge depends on the material. The drilled surface (the conical surface and especially the cylindrical surface) is strongly affected by the built-up edge, and a good drilled surface is obtained when the formation of the built-up edge is suppressed in the vicinity of the margin.
