| 摘要 |
PROBLEM TO BE SOLVED: To provide a ring bit capable of preventing consolidated silt from sticking to the front end.SOLUTION: A ring bit 1 has plural blade chips 3 which are fixed to the front end of a cylindrical bit body 2 for drilling the ground. The ring bit 1 also includes: a pair of inner periphery overhang pieces 5 extending from the inner peripheral surface of the bit body 2 toward the shaft center; and a pair of inner periphery blade chips 6 which are fixed to the inner periphery overhang pieces 5 respectively for drilling inner side than the blade chips 3 in a doughnut-shape. The plate of the inner periphery overhang piece 5 is fixed in parallel with the shaft center of the bit body 2. The overhang length of the inner periphery blade chip 5 from the inner peripheral surface of the bit body 2 is arranged to be larger than 1/3 of the inner diameter of the bit body 2.SELECTED DRAWING: Figure 1 |
