[asid61]

I generally design very specialized components such as gearboxes or drivetrains that include a lot of machined parts, just to see if an idea is feasable. As a result, I keep things organized for myself, but without part numbers (not that many COTS parts, you see). For example, I have a "gears" folder which has inside of it folders for "20p"(20 pitch), "24p", "32p", "metric" (usually 1 module), "sprockets", and "pulleys". Inside the "20p" folder I have gears labled as, say, "18t 20p 0.5in hex" to denote the pitch, tooth count and bore. This usually makes each gear unique when I copy them to other folders. I just keep things organized by name for regular parts, although I would rather have parts in folders by manufacturer for ease of use when I make things for the team.

For machined parts, part numbers all the way.