Large Screw-Top Box

This is a box I've created utilizing techniques that I learned for drawing screws and nuts [in SketchUp] during the last contest. I know there are a few screw-top containers out there already, but now there's one more. 

The screw top portion is a little different than most I've seen; it's more like a machine bolt's profile rather than a bead running around a wall. I went with a cylinder for the basic shape because it was easiest form to draw once I had made the round screw portion. In the future I may try more complex shapes for the base.

This is my third iteration of the box. The first was too loose and the walls too thick. The second was too blocky (not round enough), off-center and took too many turns to close. This third version closes tight in about one rotation, is rounder (120 sides to the circle) and has 1.5mm thick sides.