| 摘要 |
<P>PROBLEM TO BE SOLVED: To stably perform the guide action of an edge part by first and second margin parts even in a double margin type drill for largely forming a thinning part. <P>SOLUTION: When viewing the edge part 12 from the tip side in the axis O direction, a crossing angle θ of a straight line X for connecting a point 54A and the axis O positioned on the most drill rotational directional T front side in the second margin part 54 and a straight line Y for connecting the outer peripheral end 42A and the axis O positioned in a land part 50 in a crossing ridgeline 42 of a tip flank 13 and the thinning part 40, is set in a range of -5° to 10° with time of positioning the straight line X on the more drill rotational directional front side than the straight line Y as positive. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
