Klipper Nozzle Change
These are the things to do to change nozzle when the printer is using Klipper firmware. Mine is an Ender 3 but should be similar for other printers.
* Heat up the nozzle
* Retract the filament
* Unscrew the nozzle (eg. .8)
* Clean
* screw in the new nozzle (eg. .4)
* Calibrate Z