I've added a new bigger version of the knob, for even quicker up-and-downings. Pictures are of both the smaller and the bigger knob.
This two piece part replaces and adds to the acrylic stock cover on the Creality CR-10's Z-axis lead screw, which has quite a bit of slack. At least it had on my machine.
This design fits much better, and also lets you manually control the hot end up and down (when steppers are disabled), which I have found to be very handy at times. For example when stopping a failing print or first layer, you can easily lift the hot end by hand to give you more working space and a better view of the piece.
I hope someone else has use for it as well. Please share if you make one.
Print the knob upside down. No supports needed for both prints.
Pictured parts are printed in Das Filaments Feuerrot PLA at 210°C/50°C on the Creality CR-10.
You can probably get away with less, but I printed with a 30% infill just in case.
Just swap the acrylic stock part with the freshly printed cover plate, using the stock screws. The knob then simply screws onto the lead screw until it's snug enough to let you control both up and down movements with it.