| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold forming tap for a blind hole capable of forming a internal thread on the blind hole, and having durability. SOLUTION: This cold forming tap for the blind hole is provided with a taper-shaped introducing part 11 gradually enlarged toward an axial rear part, on its tip part, a complete screw part 12 having plural lobes 1a at equal intervals in the circumferential direction is mounted continuously from the introducing part 11, each lobe 1a is provided with an axial oil groove 3 on its intermediate part, the introducing part 11 and the complete screw part 12 are spirally connected in a state of being separated form each other by the oil grooves 3, and the introducing part 11 has a dimension of approximately one heap of the complete screw part 12. As the oil can be easily and fully distributed to the tap, the heat generated in machining can easily escape, the cooling effect is improved, and the frictional resistance is lowered, whereby the durability can be improved. Further the internal thread can be surely formed to the bottom of the blind hole.
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