Our collection of 3D-printable gear mechanisms would be incomplete without the model of a screw gear drive. Screw gears are regular helical gears mounted on non-parallel, non-intersecting shafts. They are also known as crossed helical gears.

The shape of this screw gear drive was inspired by the DNA molecule. In this particular model, there are three gears mounted at 45° to each other, but the shaft angle can be any number between 0 and 90°.

The .STL files for this and many other models can be downloaded from http://www.otvinta.com.