1/2" hex shaft collar (#4-40 screw-down)

thingiverse

This two-part shaft collar pairs perfectly with #4-40 x 1" socket head screws and 1/4" #4-40 nuts - lock nuts are highly recommended.\r\n\r\nWhile offering less grip than a conventional metal shaft collar, it still manages to get the job done for light-to-medium duty tasks.\r\n\r\nFor jobs that don't require any screws at all, take a look at this ziptie-based design: https://www.thingiverse.com/thing:3377384