For my metal object, I wanted to see how easy it was to create a gear from scratch. My plan to create the teeth was to drill a bunch of evenly-spaced holes in an aluminum square, and then I used a Dremel to finish cutting out the gear shape. My first attempt with making a gear didn't go so well. I marked my holes too close to the edge, and the drill bit kept slipping and wouldn't grip the aluminum properly. The fix was simple enough: I cut out another square of aluminum and marked holes for a smaller gear. After I had drilled the holes in one square, I used them as a guide to mark the holes in the other square.
Because I had already drilled the centers in the squares, I ended up with two slightly lopsided gears, but they were still able to rotate, and filing the teeth helped even them out. I also cut a diagonal aluminum plate to mount the gears on. I tapped two holes to fit bolts that held the crooked gears in place, but allowed enough wiggle room to allow them to still turn. For my first attempt at making gears, I am pretty happy with how they turned out. I definitely should've been much more precise with my measuring, and I should've drilled the centers after I had cut the gears out.