DRILL

PROBLEM TO BE SOLVED: To prevent a finished article from getting surface coarseness and spoiling quality when swarfs strike on the inner face of a finished hole even in the case of producing slightly extended swarfs.SOLUTION: A swarf discharge groove 5 is formed in the tip outer periphery of a drill body 1 rotated around the axis O to provide the tip of a wall face 5a directing in the drill rotation direction T of this swarf discharge groove 5 with a cut blade 6, and the tip outer periphery of a wall face 5b directing reversely to the drill rotation direction T of this swarf discharge groove 5 with a swarf control wall 9 smaller in the outer diameter around the axis O than in the outer diameter of the cut blade 6 with the tip edge located on the rear end side of the cut blade 6 in the axis O direction to extend oppositely in the drill rotation direction T to face the rake face of the cut blade 6.SELECTED DRAWING: Figure 4 【課題】延び気味の切屑が生成されるような場合でも、切屑が加工穴の内周面に当たって仕上げ面粗さや加工品位が損なわれるのを防ぐ。【解決手段】軸線Ｏ回りに回転されるドリル本体１の先端部外周に切屑排出溝５が形成され、この切屑排出溝５のドリル回転方向Ｔを向く壁面５ａの先端に切刃６が設けられるとともに、切屑排出溝５のドリル回転方向Ｔとは反対側を向く壁面５ｂの先端外周部には、軸線Ｏ回りの外径が切刃６の外径よりも小さく、かつ先端縁が軸線Ｏ方向において切刃６よりも後端側に位置して切刃６のすくい面に対向するようにドリル回転方向Ｔの反対側に延びる切屑制御壁９が設けられている。【選択図】図４