This is a simple thumbnut for nylock-type friction action.

I made this for the adjustable bed on my printrbot GO, but it is scalable for a variety of uses.

You can customize the height, diameter, internal diameter, height of the knurled portion and number of knurls and includes a nopheads polyholes module for properly sized internal diameter but with an adjustment (85%) so that you can run a tap through the hole to cut threads. I found that when I printed them in Taulman 618 nylon that i could also just force them into the threaded rod without cutting threads for an even tighter fit.