| 摘要 |
A reamer edge 16 is provided at a chamfer part 13 of a thread forming tap. When the tap is pulled out after the internal thread 22 is formed, a seam portion 23 present at the crest of the internal thread 22 is cut off whereby, even in a blind hole, formation of internal thread 22 and cutting of seam portion 23 are performed in a single process. The formation of the internal thread 22 and processing of inside diameter portion are thus achieved in a single process so that concentricity in ensured. Further, even if there is a deviation in the diameter of the hole 21 before threading, the inside of the internal thread 22 is processed to a constant value. <IMAGE> |
