Metric vs. SAE and supplies
It's rare that I buy hardware .... REALLY RARE. I've been spending the last 40 years saving every screw, nut and washer and have it all cataloged into around 150 divided plastic parts drawers, to the point that if you ask me for a 6-32 brass screw, 1.5 inches long with a Torx pan head, I can lay my hands on it in under 30 seconds.
Collecting hardware this way has one major advantage: I can produce nearly any item of hardware you need, which is great for replacing missing hardware and build small and medium sized projects.
Of course, it has a couple of disadvantages: (1) you usually don't have enough of any one screw (washers and nuts usually aren't problems) to handle production runs of a project and (2) boy, oh, boy does it take a long time to sort hardware; I usually keep a coffee-can-sized container on the bench for loose hardware and if I'm in the midst of scrapping a lot of stuff, I end up with a gallon can (sorry about the Imperial measures, folks) if stuff and it does take several days of intense sorting to get it all put away.
But, I have hardware in both SAE (Imperial) and metric, all the way from the tiny 0-80 and even tinier screws found in wristwatches (it's amazing how a stock of those can come in handy) all the way to the big stuff used on machinery. I know that a lot of folks, when they harvest parts from equipment, just toss away the hardware. What a waste!
Dean