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