Summary

After scouring for a reliable 1/4 - 20 thread on the internets and coming up empty I decided to make these from scratch. I use them in my Jack Skellington articulated hand extender: http://www.thingiverse.com/thing:1809355
They are so dang handy I had to post them. The threads are designed to be boolean-subtracted from your solid mesh so that you can use common Quarter inch metal bolts as fasteners. Your can also print your own nuts and bolts, which work surprisingly well.
Enjoy!