The perfect mod for visualising your extruder motor's movement!
This wheel magnetically attaches to the back of a nema 17 stepper motor. It requires two 2x1mm magnets. I recommend you superglue them, into the two slots on the top of the shaft. the slots are slightly large for the magnets (to leave room for error on low quality printers) but that shouldn't matter as long as you glue them in place well. Be careful with the superglue!
You might be wondering why I didn't make it so there is just one magnet that connects to the centre of the shaft. I did that because the actual shaft isn't magnetic. But the ring around it is - so they were the only place I could connect the magnets.
A video of it in action is here!!!! https://www.youtube.com/watch?v=qIqxJ6YP2oQ