| 摘要 |
PURPOSE: To reduce a noise, to enhance working efficiency, and to lengthen the service life by joining a drill head and an insertion end constituting a drill tool by a retaining element together with a shank divided into a plurality of segments. CONSTITUTION: A drill tool is composed of a drill head 1 having a hard metallic cutter 1a, a shank 2 divided into three equal segments 2a, 2b, 2c and an insertion end 3 having a lengthwise directional groove 3a. The drill head 1 and the insertion end 3 are made mutually integrally rotatable by a pipe 4 via respective joining planes 1c, 3b and a recessed plate 4c of the pipe 4, and are relatively displaceably interconnected in the axial direction in a prescribed range. Instead of the pipe 4, it may be constituted so as to use a rod penetrating through the shank 2 as a retaining element. A natural frequency is not excited in respective parts 1, 2, 3, and kinetic energy can be optimally transmitted. |
