THE DISAMBIGUATOR: A Threaded Insert Accommodates Dissimilar Screws

摘要

Like a carnivorous plant, the imperial threaded hole lurks in wait for its prey: a similarly sized metric threaded post. A male metric fastener can easily mistake the imperial female thread for its perfect mate. A standard six-millimeter (M6X1) metric screw will freely turn nearly a full turn into the common quarter-inch (1/4-20 UNC) threaded hole before the mismatched threads mesh into some resistance. A seasoned user may realize that the fastener is mismatched. A university student in the workshop, a physicist in the optomechanical lab or a DIY hobbyist at home are likely to use a tool to "help" the unwilling screw continue threading in and jam it in, break it off or strip off the threaded hole.