
Fan Timer Knob
thingiverse
Woods 59717 fan timer perfectly fits the bill. Check it out here: https://www.amazon.com/Woods-59717WD-60-Minute-Decora-Mechanical/dp/B001XCWLX8 It works seamlessly with a 5mm shaft, and the measurement from the flat of the register is exactly 4.1mm. When using this timer with your printer and filament, you might need to apply a small amount of glue to get it just right.
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