| 摘要 |
A cutting tap (1) comprises a threaded portion (3) including a lead (3a) whose thread diameter gradually decreases toward a front end of the lead (3a), a complete thread portion (3b) continued from the lead (3a), and four flutes (3c) arranged at equal intervals in a circumferential direction. In the cutting tap (1), a first cutting edge portion (4) for processing a prepared hole is formed at a front end surface of the lead (3a), and a second cutting edge portion (5) for finishing a minor diameter of an internal thread is formed in a part of an outer periphery of the complete thread portion (3b), the second cutting edge portion (5) being one or more pitches long. The cutting tap (1) can perform processing of a prepared hole, tapping, and finishing of a minor diameter by a single step, and can also perform tapping even if a prepared hole for an internal thread is a blind hole or the like and does not have enough space. <IMAGE> |
