I like watching craftsman and maniac Ronald Walters' woodworking videos for two reasons. Number one is his skill. Number two is because he sounds enough like Parks & Recreation's Ron Swanson that I half-expect him to say things like "Turkey can never beat cow" or "Kendra, I think I will have that third steak."
In any case, if I showed you a bunch of plywood gears like the ones pictured above, you'd probably ask where I had them CNC'd. But Walters cuts his teeth the old-fashioned way: With a freaking scroll saw, following along on a pencil line. His accuracy is pretty nuts—if he were off by a millimeter here and there, he probably wouldn't be able to rotate his pin gear and ring gear assembly at this speed:
If you're wondering why the holes around the circumference, Walters is planning to incorporate the gear into some kind of marbles machine.
You can catch more of his videos here.
Wait, wait. I'm worried what you just heard was, "Give me a lot of bacon and eggs." What I said was, "Give me all the bacon and eggs you have". Do you understand?