What is the recommendet procedure for changing the nozzle?
We recommend using the tape as it prevents the hotend form leaking at the heater block, even tightening whilst hot can cause a leak over time as the hotend vibrates/heats up/cools down.
It's optional though, you may be able to get away with the 'tightening whilst hot method'.
I read that too about PTFE tape. I think this might be recommended because of the E3D v6-like parts that we got (ie. they are not genuine E3D). I've found Tom's 3D channel on YouTube really useful, starting at 4:22 on this video https://www.youtube.com/watch?v=tDq1Du9gaWM he shows how to change a nozzle, which many other guides also indicate about leaving the nozzle slightly loose then fully tightening it while up at temperature.
From what I've read, at PLA printing temperatures a pure PTFE tape should be safe, and I print in a very well ventilated garage. I expect we also got shipped cheap tape, so no idea what else might be mixed in there. I think getting a good tight fit between the nozzle and heat break if they have both been machined flat and square to each other, and tightened at temperature, then the tape should not be required. I won't be fitting tape when I next change the nozzle and if I do have any leaks or jams I'll upgrade to a well machines nozzle and heat break.
I was reading that PTFE tape is not recommended as the temperatures can cause the tape to melt and give off toxic fumes:
Does anyone know why the build manual suggests to use ptfe tape around the nozzle? @Makertech
When googling for how to do this elsewhere for E3D v6 hotends, all the ones I've seen say to do this while the hotend is hot and none say to use tape?
I don't know what Makertech recommends, but I was able to replace my nozzle by putting some of the PTFE Thread Tape around the new nozzle and then unscrewing the current nozzle and putting the new one in. I would recommend first heating your nozzle up and removing any filament first though before putting the new nozzle in.