WordNet records no synonym and no antonym for setscrew. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a screw that is used to adjust the tension on a spring
a screw (often without a head) that fits into the boss or hub of a wheel or cam etc. and prevents motion of the part relative to the shaft on which it is mounted
Synonyms, antonyms and the broader and narrower relations for setscrew come from Princeton University’s WordNet. Full sources and licences.