[evanlivingston]

This is, in practice, the utility of the widespread use of CAD. Many manufacturers of parts distribute CAD models of those parts.

For example, McMaster-Carr have CAD models (in various formats) for nearly every single part in their catalog.

A designer/engineer can import those parts and then either create drawings referenced off of those parts, or mate/join those part using reference geometry. That is to say, the API is the geometry, and the CAD software provides good tools for interacting wit that API.

[0_____0]

MCM's 3D parts are also great starting points for stuff you'd like to print for prototyping. I just printed off a bespoke belt pulley using an MCM model as a base this past week. Added a bunch of specific mounting features I need for my application. It's an inferior part printed in FFF, but it'll work for now.

[skykooler]

And the nice thing is, if it breaks and you determine you need a better one, you can order the part from mcmaster and you already know it'll fit.

[RobotToaster]

Also a great way to get weird threads and connectors. Need a NPT thread? Just import a NPT cap.