I wanted to make a wood and black pipe style shelf in my nerd cave with my son.  I didn't want to buy all the fittings when I have a printer that would do exactly what I needed and make it a small enough diameter that it wouldn't look too clunky and take up space.  I cannot guarantee the strength if using in a horizonal manner, but it has been holding up just fine as feet/attachments to my shelves.

The thread is ½" NPT.