| 摘要 |
<p>A high durability taper tap for pipe threads which can cut threads in a pipe made of a hard material having the hardness of approximately 50HRC is provided. The sum SIGMA gamma of the width angle of cutters is set approximately 130 DEG . By setting the width of each cutter large, a high strength and rigidity are achieved. Since the rake angle of the cutting edge alpha is set approximately -20 DEG , the cutter angle beta defined by the rake face 8 and the peripheral relief becomes more than 90 DEG so that the strength and rigidity of the cutting edge 6 are enhanced. In addition, since the taper of the bottom of the flutes 4 is set in a ratio of 1/16, approximately equal to that of the taper of the thread portion 2, the rake angle alpha of all of the cutting edges 6 from the smaller end to the larger end of the thread portion 2 becomes equal so that all of the cutting edges 6 can equally cut the threads. Further, the diameter Df of the bottom of the flutes of the top end portion 1a is set approximately 60% of the smaller end of the thread portion 2, which is larger than that of the common tapping tool. Owing to this configuration, the taper tap for pipe threads of hard material having an excellent strength, rigidity and hard wearing property can be achieved. <IMAGE></p> |
