| 摘要 |
PROBLEM TO BE SOLVED: To permit the working of inverted tapered shape by setting an outer diameter of a part to be worked larger than the outer diameter of an axial part, and forming a shape of an end of the part to be worked at an axial part side into a projecting arc shape formed with a diameter to be reduce toward a rear end side thereof. SOLUTION: Shape of each cutting blade 5 of an end mill 1 is formed into a projecting arc shape at a rear end side, namely at an axial part 3 side in a cross section passing through the center axis of the end mill 1, and a tip side of the projecting arc shape is formed into a linear part 7 along the axial direction. At the time of rough working of a tapered hole with the linear part 7, cutting radius is set large at the tip side, and the cutting radius is reduced step by step at the rear end side in the axial direction. At the time of finishing the tapered hole, in the point contact condition that the projecting arc part 6 contacts with a work piece at one point, the end mill 1 is moved backward in the axial direction and while the radius of revolution is gradually reduce. With this structure, inverted tapered hole can be formed. |
