So, I made 25 1" split rings in about twenty minutes; they're for hooking wire to wire, which I do a lot, and I may well need different sizes for different wire, but that just means finding a different dowel. It's the same technique as making jump rings, only you cut every other wire (when I do that for jewelrymaking I grind the cut ends smooth; bought split rings are made with either square or half-round wire, but I'm stuck at about 1209 in my metal fabrication technique). It's also the same technique Rennies/SCA folks use for making rings for chain mail, only that needs to be done perfectly symetrically or you can't make actual mail.
That is: drill a hole the size of your wire (the same stuff you'd use for making raspberry trellis) about 1" in from the end of your dowel, cut a piece of wire 2-3 feet long, and make a 1/4 right-angle turn in the end of the wire. Insert that in the hole, and then turn the dowel slowly while holding the wire firmly so it bends around the wire. When you get to the end of the wire, use needle-nose pliers to curve the last bit around the dowel. Pop the bent wire out of the hole and slide the bent wire off the dowell by pulling on that end. Use bullnose wirecutters to cut every other loop at even intervals (line your first cut up with the end of the wire); if the last ring is a little short or long, take a deep breath and remember: it's a chicken coop. Nobody's grading you on this.