| 摘要 |
PURPOSE:To facilitate the processes of connecting together a shank and a center drill in a core drill and automatically centering the center drill, by connecting the shank and the center dril by screws. CONSTITUTION:A male screw portion 45 on which a cylindrical cutting tool is screwed in is formed on the periphery of a shank 30 in such a way as the cutting tool may be tightened more as the received cutting force increases, and a female screw portion 42 and an inner bottom portion 44 are formed on the inner periphery of the shank 30. A male screw portion 40 which is to be screwed in the female screw portion of the shank 30, a portion 38 not threaded and a tapered portion 36 are formed on the base end portion of a center drill 32. When the center drill 32 is screwed in the shank 30, the tapered portion 36 is positioned in the inner bottom portion 44, and its centering is achieved automatically. |
