| 摘要 |
PROBLEM TO BE SOLVED: To let prepared hole working, tapping and inner diameter finishing be accomplished on one process, let lapping by carried out even when there is no margin in the prepared hole of a female screw due to a bottomed hole and the like. SOLUTION: The cutting tap has both bevel leads in which the crest diameter of each thread part is gradually made small in diameter toward its tip end, and complete crest parts 3b continued to the bevel leads, and concurrently, has dour grooves 3c equally disposed in the circumferential direction. In this case, each first edge part 4 for machining prepared holes is formed in the tip end face of each bevel lead, and concurrently, each second edge part 5 for finishing the inner diameter of a female screw thread is formed in one part of the outer circumference of each complete crest part in such a way as to be longer in length than one pitch. |
