| 摘要 |
PURPOSE:To prevent a blade from floating out of a tool body to perfection in a mechanical manner, by forming an internal thread in an outer circumferential part of the tool body at the central side, while also forming an external thread engaging the internal thread in an inner circumferential part of the blade. CONSTITUTION:In an outer circumferential part of a hob body 1, a screw part 11c is installed in the other end, while a trapezoidal external thread 11d is formed in the middle. A screw thread's axial sectional form of the thread 11d makes a side face at the side of a flange part 11b to be an almost nearly right angle with the axial direction and also makes a side face at the side of the screw part 11c a trapezoidal form being tilted to the side of the flange part 11b whereby a range of the screw thread is made so as to be narrowed at the central side. And, plural blades 12 are disposed in cylindrical form, and a trapezoidal internal thread 12c engaging the trapezoidal external thread 11d of the hob body 11 is formed in the inner circumferential part. With this constitution, floating of these blades 12 from a tool body is completely preventable in a mechanical manner. |
