Salt shaker (OpenSCAD)

**LATEST VERSION**: https://www.thingiverse.com/thing:3548762

A salt shaker, made with OpenSCAD.

The idea was to use the ```linear_extrude``` module with the twist parameter to create a "screw". It turns out that it's not a good idea. That feature is quite messy, create concave surface and it's hard to control.

I found a screw library http://www.thingiverse.com/thing:8793 but I'm not satisfy with the result. It doesn't respect its parameter. The screw is longer then its length parameter