Well, it also depends on whether you are using a home desktop plastic extrusion type printer or a big expensive selective laser sintering printer (SLS). A home printer has to have more space between the parts to prevent them from fusing together.

For example, on the high end SLS printers that use a nylon powder, you can have very intricate moving parts and fully working chains, gear systems, rotating tires, etc. etc. with only 0.5mm between pieces required for them to not fuse together. Yes, that's HALF of a millimeter of clearance is all that's needed, so tiny intricate fully moving creations are possible, as well as elaborate puzzle boxes and intricate chainmail are even possible. And there is no assembly required. The item is just removed from the powder, cleaned, and then all the moving parts will be freely moving right out of the printer!