Captive Nut
thingiverse
The nut is screwed onto one of the large threads, and then the two large parts are screwed together. Meant to look like an illusion when the big threads line up, glue them in place by putting a few drops of superglue on the inner thread when it does line up.
Download Model from thingiverse
With this file you will be able to print Captive Nut with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Captive Nut.