| 摘要 |
A tap having a reamer edge which is provided at a chamfer part, so that when the thread forming tap is pulled out after the internal thread is formed, a seam portion present at the crest of the internal thread is cut off, whereby even in a blind hole, formation of internal thread and cutting of the seam portion are performed in a single process, and formation of an internal thread and processing of an inside diameter portion are achieved in a single process to obtain concentricity in line with each other. Further, even if there is a deviation in diameter of the hole before threading, the inside of the internal thread is processed to a constant value.
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