| 摘要 |
The tap for producing an internal helicoidal thread comprises a rigid body (3) whose radial dimensions are less than that of the tapped hole. The body supports several small, regularly spaced, rotating peripheral cylinders (4,5,6) mounted in peripheral cavities (7). Each of the rotating cylinders is provided with annular cutting threads (15). These threads are not spiral but purely circular and separated from each other by a distance (d) equal to the thread pitch. The coaxial annular threads have a common axis inclined to the tap axis by an angle equal to the helix angle of the tapping. Each of the cylinders overshoots the body peripheral surface so as to allow pieces staying between the rigid body to fall into this space.
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