| 摘要 |
PURPOSE:To improve the centripetal characteristic and the cutting stability, and improve the surface roughness of the wall surface inside of a hole remarkably to improve the accuracy of the finish hole remarkably. CONSTITUTION:A burnishing drill 1 consists of a cylindrical shank 11 and a drill body 12 connected to the shank 11. Tips of a first small diameter part 8 and a second small diameter part 9 and a third small diameter part 10 of the tip of the drill body 12 are formed with drill blades 20a, 20b, a reamer surface 221a and a reamer blade 22a. The reamer surface 21, which is arranged in the rear end side than the drill blades 20a, 20b and the reamer blade 22a in the drill shaft direction and which is extended outside in the radial direction, is inclined so that it is inclined outer of the radial direction as it is arranged more rear in the drill shaft direction, and that it is separated from the drill axis as it is arranged more rear in the direction of rotation of a drill. Irregularity of the inner wall surface of a lower hole, which is drilled by the drill blades 20a, 20b and the reamer blade 22a, is therefor evened by the reamer surface 21a at the time of drilling to improve the surface roughness of the finish hole remarkably. |
