I was looking for a way to use brass hinges on my garden gates. I solved the problem of attaching a flat hinge to the round ½ inch conduit by attaching a piece of ¾ inch aluminum angle. The angle is bolted to the conduit with stainless #8 bolts that I already had on hand. The hinge is bolted to the other side of the angle. The biggest hassle is making sure the two pieces of angle for the hinges are aligned. I clamped the pipe and angle in a vise for drilling.
Great idea! I can see that being a useful technique for all sorts of things. Thanks for sharing!