Self Tapping Inserts for Plastics
The course external thread of SPIROL's self-tapping insert forms an internal thread within a molded or pre-drilled hole during the installation process into a plastic assembly. They are thread-forming Inserts best suited for softer thermoplastics or thermosets. Self-tapping inserts provide the best pull-out resistance for a post-mold installed insert, yet generally cost more than their post-mold counterparts. The external threads are designed with a thin profile to minimize induced stress in the plastic and have a relative coarse pitch to provide the maximum plastic shear surface to resist pull-out. Installation torque is not a problem in that tightening increases the friction between the plastic and threads, and the larger diameter of the external insert thread increases the frictional surface. Back-out torque performance relies totally on the greater surface area of the external insert thread and the tension between the threads and plastic.