Abstract: A throw-away rotating tool includes plural protrusions formed in a part of an outer peripheral wall of a projecting coupling portion. Since the twist angle and a twist direction of the protrusions are set in such a way that with relative rotation when coupling the projecting coupling portion and erected portions together, due to the reaction force received by the protrusions from inner peripheral walls, the projecting coupling portion is pulled to the rear and side of the erected portions and the projecting coupling portion is stably held between the erected portions. Since the number of portions that require stringent dimension control and high machining accuracy can be reduced, productivity can be improved.

Abstract: A throw-away rotating tool includes at least two grooved portions 13b, 13c formed on each of erected portions 13 and at least two protrusions 26, 27 for fitting into and removal from respective grooved portions 13b, 13c and projected from a projecting coupling portion 23, and the grooved portions 13b, 13c are formed asymmetrically about an axis O and the protrusions 26, 27 are formed asymmetrically about the axis. Thus, the direction in which the projecting coupling portion 23 can be coupled to the erected portions 13 is uniquely determined. Consequently, variations in lip height and run-out can be minimized. As a result, occurrence of a bend and an increase in machined hole diameter during drilling can be prevented, thereby making it possible to minimize variations in machining accuracy and tool life.

Abstract: A throw-away rotating tool includes plural protrusions 24a formed in a part of an outer peripheral wall 24 of a projecting coupling portion 23. Since the twist angle and a twist direction of the protrusions 24a are set in such a way that with relative rotation when coupling the projecting coupling portion 23 and erected portions 13 together, due to the reaction force received by the protrusions 24a from inner peripheral walls 13a, the projecting coupling portion 23 is pulled to the rear and side of the erected portions 13 and the projecting coupling portion 23 is stably held between the erected portions 13. Since the number of portions that require stringent dimension control and high machining accuracy can be reduced, productivity can be improved.