Learn to design and assemble parts with screw threads and gears for 3D printing in this comprehensive tutorial. Explore the power of FeatureScript in Onshape to create custom tools for generating screw threads and spur gears. Discover how to measure threads, adjust clearances, and model a functional fidget toy. Master assembly techniques including fastened and revolute mates, as well as gear relations. Follow along to create a working mechanism, considering the specific requirements for 3D printing these intricate features. By the end, gain the skills to design, print, and assemble your own custom parts with complex geometries.