| 摘要 |
PURPOSE:To put a male threaded part in certain engagement with a thread formed on the inner wall of a work to be processed, by providing an axially directed rake angle at the tip of at least one of the cutting edges, giving this rake angle a value differing from the axially directed rake angle at the tip of other cutting edges. and thereby preventing irregular swings of the male threaded part during the processing. CONSTITUTION:An axially directed rake angle theta1 is provided at least at the tip of at least one of a plurality of cutting edges 14a-14c formed in a male threaded part 12, wherein the rake angle shall have a value differing from the axially directed rake angles theta2, theta3 at the tips of the other cutting edges. Therefore, the machining load on the cutting edge having different rake angle becomes different from the machining load on the other cutting edges, so that an unbalance is generated in the tap radius direction components of the machining loads applied on the cutting edges, which causes progress of the processing in the condition that a specific part of the male threaded part 12 is pressed to the inner wall of the work stronger than the other parts are. This further ensures that the thread on the work is engaged with the male threaded part 12. |
