Molded-in threads

Molded-in threads can be used when frequent assembly and disassembly are not required. Mechanical thread-forming operations are eliminated in that way.

Both Internal as well as external threads are commonly used.

When designing molded-in threads, the following rules must be taken into account:

1. Maximize the root radius to reduce stress concentrations

2. Thread run-outs should preferably be rounded off to avoid cross threading and thread damage

3. Avoid tapered (pipe) threads, unless a positive stop is provided.

4. Avoid very fine threads with a pitch smaller than 1 mm, considering mold filling and tolerances.

5. Special attention must be paid to constructions in which metal and plastic mate. Differences in thermal expansion and stiffness may lead to high stresses or loosening of a connection. Sharp edges on metal threads may damage the plastic.

6. The connection must be checked for high stresses due to tightening or loosening due to creep or stress relaxation.