| 摘要 |
PROBLEM TO BE SOLVED: To provide a thread forming tap with a stable lifetime by preventing the threads of the tap from being chipped. SOLUTION: The thread forming tap 1 has a screw part 2 with a tapered bevel lead 3 whose tip is narrower and a parallel screw part 4 continuous to the bevel lead 3. By making the thread top cut height of the bevel lead 3 higher than the thread top cut height of the parallel screw part 4, the thread forming resistance in a part near the intersection point of the bevel lead 3 and the parallel screw part 4 where chipping of the screw threads may be easily generated is reduced, so that chipping of the screw threads in the thread forming tap is prevented. COPYRIGHT: (C)2004,JPO
|
