You can print threads with a 3D printer. As long as the thread is big enough. Like M10. What about smaller sizes like M3 or M2? You can just print 2.9mm-3mm hole and tap it by force with a screw but on a longer run this sucks too. Recently I have "discovered" brass threaded inserts that you can get in hundredths for cheap and just install them with a soldering iron in 3D printed parts.