Customizable Stepper/Extruder Knob

A parametric recreation of Jeff Latham's Printrbot Feed Wheel. It's basically a knob that presses onto the tip of a stepper motor's flat shaft. Makes it easier to observe the extruder's motion and gives you the option of manually rotating the shaft if need be.
All the dimensions are adjustable - handle size, shaft length, etc. Depending on the design of your printer, you may need to make changes to avoid mechanical interference. For instance, the version I printed is sized to stick out far enough that the handles won't hit the vertical frame. You may also need to tweak the shaft socket size to ensure an easy fit on your motor.
Exciting action footage: https://www.youtube.com/watch?v=CKsma1QFEoA