| 摘要 |
PURPOSE:To make it possible to remove flashes at the entrance of a hole in a same process without changing drills by providing a twisted arm according with the inside of the twisted groove of a drill for drilling a hole, providing flash removing edge at each top end portion of arms and connecting them in one body by a circular drum. CONSTITUTION:Edges 1, 2, 16 are selected according to the outer diameter 9 of used drill and the thickness 12 of a steel plate for drilling holes and the selected one is fitted along from the top end to the twisted groove and holes are drilled through for common use for the drill. Continuing to drill the through hole, feed volume is added and the cutting edge 4 of the edges 1, 2, 16 goes through the hole under removing flashes at the entrance of the hole. Then, when the feed of the drill 17 for drilling holes is returned, a cutting edge 5 goes through the hole again to remove flashes 15 at the outlet of the hole. Because of this, the cutting edges 4, 5 can be used for either of the inlet or the outlet. Hereupon, generally in case that plate thickness 12 near the outer diameter of the drill is drilled through, chip disperses and the long twisted groove of the drill is not necessary so that the twisted cutting edge for flashes can be used in common as the drill for drilling a hole. |
