Summary*** Updated cover to r3 -- adds through hole for easier motor shaft extraction. Print without supports, because easy-breakaway supports are already in the model! I wanted to use an old set of Vex wheels for my upcoming rover project. They use an annoying square axle, which is incompatible with standard DC motor shafts. Well, not anymore! This pair of pieces should allow me to mount the wheels to any stepper motor with a 5mm shaft. It has capture features for the M3 screws which are used to hold onto the shaft, and recesses for M4 nuts to clamp the wheel onto the hub.InstructionsPrint without supports! Uploaded r2 models to deal with some annoyances: hub cover screw holes are recessed so you can use a M3x25 to clamp over the wheel. Otherwise, you'll have to go with M3x30 and have excess threads sticking out. widened the captive nut slots a litle to make insertion easier. added another concentric ring for support material Press 3 M4 jam nuts into the recessed areas of the hub. Press 3 M3 jam nuts into the capture slots near where the motor shaft will go. I recommend drilling through the Vex wheel as well so you can get the hub closer to the bearings in the stepper motor. Remove the two concentric rings under the "hub adapter M3" part. These should peel away easily due to the way I modeled them. Screw 3 M4x25 screws into the hub to clamp down on the wheel, and then screw 3 M3 screws to hold onto the motor shaft.