Wheel hub - 12mm hex to 5mm

thingiverse

A custom adapter that seamlessly integrates a standard 12mm hex RC wheel onto a sturdy 5mm shaft attached to a powerful NEMA17 stepper motor. Post-printing, I simply drill a precise hole for the wheel and a separate hole for the set screw using a trusty 6-32 tap. Instead of overcomplicating things by engineering threads directly into the part, I opt for a straightforward approach - drilling a small hole where I need it most, then threading it with a tap to achieve remarkably better results.