I have been printing wheels for a kitchen draw, 20mm dia, 6 mm thick and with a radius (like a bike tyre) not a flat surface, and little stub axles of 3 or 4 mm. The start and end of the wheel (printed vertically on a raft) are a little rough, nothing serious as it will never be seen but the one change that would seem to make a difference is a finer thread of plastic. As I only want to change the nozzle my initial thought would be that this was easy, but it's full of solid plastic and needs to be tightened quite specifically (or heat it and have plastic running everywhere) and with a gap so it does not hit the Al block or damage the heat break. Do I need to take the whole assembly out, heater etc. and remove the whole thing from the X-Carriage or is there a simpler way?
No. You can better heat the block to about 185°C. Now you can remove the nozzle quite easy (don't burn your fingers ), and place another one.
My process would be 1 , heat nozzle 2 , pull Filament out 3 , unscrew nozzle (it's hot! I usually catch it in a metal lid so I can move it out the way before I forget and pick it up) 4 , screw in new nozzle, if its difficult just let it cool down to get the thread in 5 , Heat to 235(or whatever the magic temp is) to tighten up the nozzle fully 6 , load Filament and adjust temp to extrude