Creality Ender 3 users please read last update below
This two piece part replaces and adds to the acrylic stock cover on the Creality CR-10's Z-axis lead screw; It 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 you're loading filament, 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.
Works exactly the same as the earlier version I made, just with a bigger knob. This way it takes less spinning to manually up and down the hotend. Easily fluently movable with just one finger. Cover plate is the same as in the original version.
A simple quick and dirty demonstration by me of how the knob works:
And a more professional video by Chuck Hellebuyck on how to install the knob (and some other useful CR-10 (mini) mods) on Filament Friday: https://www.youtube.com/watch?v=qDG_C5y-psU&t=3m23s (3 minnutes and 23 seconds in).
UPDATES & HELPFUL COMMENTS
If you want to use the ZKNOB on the Ender 3, you don't need the cover plate, as the Ender 3 has a loose lead screw. I suggest printing Ben White's stabilizer, which holds a 608 skateboard bearing and secures the top of the lead screw, so you can safely screw up and down without having to be extra cautious.
P.S. A filament guide is necessary to use the knob on the Ender 3.
Thanks to user wonkoderverstaendige I found out there was a tiny (but real) problem with the file. Basically the knob floated a mere 0.002mm above the stem, which only caused a problem when sliced in particular way, but it had definitely a weak spot. So if yours snapped at any point, this is probably why. You should have no problems with the fixed file anymore. Sorry for the inconvenience if it got you frustrated!
Pemic: "The knob works also for the Tevo Tornado. The stock cover is not necessary. To gain a little space on the upper side of the spindle, you have to pull the Z stepper axle a little it out of the coppler."
Fort_Design: "I just wanted to let you know that this design will not fit the Anet E10. Mainly because the housing of the upper bearing on the E10 is closed on top. One would have to redesign these housings. Diameter of the spindle on Anet E10 is 8mm."
Print the knob upside down. No supports needed.
I used 3 perimiters and a 30% infill, but you could go higher for extra strength. I've been using mine on a daily basis for months now and I haven't had any problems yet.
Pictured parts are printed in Das Filament PLA at 210°C/50°C on the Creality CR-10.
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.