| 摘要 |
PURPOSE:To cut a large circular concentric hole by installing a tapered inserted body for positioning which is inserted into a previously cut hole on a workpiece, onto the top edge of the shank of a drill unit and positioning a hole saw by the inserted body. CONSTITUTION:A hole saw 2 having an attachment 15 and a pair of cutters 8 is installed onto an electrical twist drill 1 through a shank 5. The tapered inserted body 20 at the top edge of the attachment is attached into a previously drilled hole 3a, on a workpiece 3, and the nonrevolution state is maintained, and the twist drill 1 is positioned. The cutter pieces 10a and 10b of the hole saw are revolved by the revolution of the twist drill 1, and a large circular hole 3b concentric to the hole 3a is cut on to the workpiece 3. |
