Box Fan Knob

It being summer now, my local hackerspace Sprout has started needed ventilation. We have a box fan (and, over the years, I've had several) that had no knob. Did we lose it? Did it break? Did the knob fairies make off with it? Who knows. I do know that my fingers hurt from trying to turn it and I never seemed to have a pair of pliers handy. I did have a Thing-o-Matic, though...

I started by downloading Stove Knob by wizard23 and while it did technically work, the hole for the shaft was too lar