| 摘要 |
The process is carried out using a press tool which has a plurality of dies which are arranged around a longitudinal axis and are radially displaceable with respect to this axis. The radially inner surfaces of the dies correspond to segments of the conical thread to be pressed. During pressing of a conical thread in a cylindrical workpiece, the dies are first drawn apart in the radial direction and the workpiece is then pushed between the dies, along a length which corresponds to only a few thread turns. The dies are then pressed toward one another in order to press into the workpiece a short conical thread in which only the first thread turn may be formed to its full depth. After the dies have been drawn apart, the workpiece is displaced between the dies through a further length which once again corresponds to only a few thread turns. When the dies are pressed toward one another again, the previously pressed thread turns are pressed deeper into the workpiece and additional thread turns are formed. This process is repeated several times until the conical thread has been pressed to the predetermined total length. Each time the dies are drawn apart, the workpiece is rotated through an angle which corresponds to part of the circular sector of a die, in order to avoid throwing up a burr between the dies which have been pushed together. An apparatus suitable for carrying out the process has an electronically controlled hydraulic unit which draws apart and presses together the dies and feeds and rotates the workpiece as a function of the diameter of the workpiece. |
