Metallic threaded insert for plastics workpieces - has external multistart anchoring thread and internal opposite thread for screw

摘要

The metallic threaded insert is fitted into workpiece holes. The hollow insert has a tapped central hole and an external screw thread. The external screw thread pitch on the insert opposite to the internal screw thread pitch. The pitch angle of the external thread is greater than that of the internal screw thread. The external multistart screw thread has diametrically opposite areas without screw thread. The insert is held firmly in its seat and is not readily loosened owing to the opposite pitch angle.