Yes, I know there's a cool library (Belfry OpenScad Library, v2) to achieve all sorts of mechanical parts, but sometimes someone wants to tinker around for themselves.
The best working screws with my experiments are the ones with two circles spinning around upwards with the linear_extrude() function in OpenSCAD.
Feel free to have a glimpse at the code.

The spring is printed without support and that was a bad choice - I gave it another try with support everywhere to stabilize the distance between the nozzle and the print. Fiddly to get the support out, but nice result. Photo follows...

As sometimes a rough mixture of german an english words for the variables :-P