This is a modification I made to my Voxel Ox 3D Printer Z axis, which synchronizes the Z leadscrews via a shaft and helical gear transmission. It prevents the two Z leadscrew from getting out of adjustment relative to each other, and uses a single Z motor instead of two. This build is just documenting the specific changes I have made to the Z-axis, since the frame and other axes are still from the original Voxel Ox design.

Attached to a scroll saw you can cut nested wooden spirals with this jig. Make two, three, four ... interlocking spirals that unwind/unscrew. Fascinating toys or art objects!