This Instructable shows the basic steps of how to attach an old and beat up found-by-the-side-of-the-road oil cap onto a cheap belt buckle.
The saga: Ok, so its not much of a saga. I was in town about a week ago, and one of my friends randomly hands me this old beat up oil cap and tells me that he found it on the side of the road, and that I should carry it for him. The cap languished in the bottom of my backpack for a few days, and then I unearthed it while looking for my awesome headphones i made . Upon seeing it, this idea popped into my head. Soooooooo..... here we go!
This buckle is a a great visual pleaser, plus it makes a great gift for geeks and gear-heads alike.
Note: My oil cap was plastic, so I just used a screw to attach it. Your cap could be metal, or both metal and plastic. It is kind of open-ended how you attach it, but epoxy or other things would great too.