Wheel hub - 12mm hex to 5mm

Wheel hub that mounts a standard 12mm hex RC wheel to a 5mm shaft on a NEMA17 stepper motor. After printing, I use a 6-32 tap to thread the hole for the wheel, and a hole for the set screw. I use inexpensive 6-32 machine screws from my local hardware store. I could try to engineer the threads into the part, but I've gotten much better results by just adding a small hole into the part where I want the threads and then thread them with a tap.