| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To improve surface roughness by preventing an inner wall surface of a processing hole from being damaged while preventing the curvature of the hole due to drill deflection by a guide part. <P>SOLUTION: A chip discharge groove 4 is formed from a head end flank 3 to a rear end side at an outer circumference of a shaft-like drill body 1 to be rotated around an axis O. A cutting blade 2A is formed at a cross ridge line part of a wall surface 4A directed in the drill rotation direction T of the chip discharge groove 4 and the head end flank 3. The cutting blade part 2 at the head end side of the drill body 1 having the cutting blade 2A has a reduced outer diameter at the rear end side in an axis O direction to the outer diameter D of the cutting blade 2A. The guide part 6 having at the outer circumferential side of the head end a maximum outer diameter part 6A whose diameter is larger than an outer diameter at the rear end of the cutting blade part 2 and smaller or the same to the outer diameter D of the cutting blade 2A is formed at the rear end side of the cutting blade part 2. The maximum outer diameter part 6A of the guide part 6 is formed into a smooth convex curved shape in a rotating trajectory around the axis O. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
