| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a drilling bit that ensures performance of discharging slime while ensuring an increased length of a guide surface in a circumferential direction to improve straight advance performance without causing an adverse effect of the slime on a pull-back operation. <P>SOLUTION: A drilling bit A is provided in which a plurality of blade bodies 2a to 2c are fixedly attached to a chip holding surface 12 of a metal base 1. The drilling bit A has guide surfaces 13a2 and 13a3 for maintaining straight advance performance between a coupling surface 11 and the chip holding surface 12 during drilling; and discharge groove surfaces 13b1 and 13b3 forming discharge grooves 13b11 and 13b31, respectively, through which slime produced during drilling is discharged. Guide surfaces 13a1 to 13a3 are inclined such that they are tapered from the chip holding surface 12 to the coupling surface 11 so as to come close to an axis line CL of the drilling bit A while the plurality of discharge groove surfaces 13b1 to 13b3 are inclined such that they are tapered so as to come close to the axis line CL of the drilling bit A as they come close to the chip holding surface 12. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
