| 摘要 |
<P>PROBLEM TO BE SOLVED: To form a machined hole of high quality with a desired inner diameter according to a diameter of a cutting edge in a work material made of copper or copper alloy. <P>SOLUTION: A cutting chip discharge groove 4 is formed in an outer circumference of a tip of a drill body 1 rotated around an axis O and made of one kind of superhard material among cemented carbide, cermet, and ceramics, or high-speed tool steel. From the inner circumferential side of the drill body 1 toward the outer circumferential side, the cutting edge 5 extended to the rear end is formed on a tip lateral edge of a wall surface facing a drill rotating direction T of the cutting chip discharge groove 4. With respect to a diameter D of the cutting edge 5, a tip X of the cutting edge 5 is radially deviated from the axis O by a gap δ within a range of 0.01×D or more to 0.03×D or less. When the drill body 1 is made of the superhard material, a core diameter is 0.2×D or more, and when the drill body 1 is made of the high-speed tool steel, the core diameter is 0.3×D or more. <P>COPYRIGHT: (C)2013,JPO&INPIT |
