THREADS

·         Threads in the molded plastic parts are commonly made either by molding in or by tapping.

·         Molded threads can be held to better tolerances than tapped threads of same size. Because tapped threads tend to have a minute chips and cracks on the surface.

·         Molded threads must start and stop abruptly.

·         Feather edges should never be specified because they are the weak areas in the part or mold.

·         External threads can be molded using a split mold, however, the excessive flash may be present which will interfere with the subsequent assembly. A chase operation can prevent this, but it is an extra and costly step.