I don't have a specific reference at hand, but it seems to me that I've seen more than one reference suggesting that PETG is better when close tolerances are needed (like the threads in that previous part).
Ok so Creality REALLY cheaped out on their screws!!! I went to install my flexible coupler last night and I stripped one of the hex nuts on the lead screw coupler. No matter what the thing would not co-operate.. I spent 2 hours trying to get it loose and ended up scrapping the coupler... I had to remove the the stepper motor and then remove the lead screw in order to get proper access to the coupler screw. I had to drill out the screw in the end. I also had trouble with another one a few weeks ago on the timing pulley shaft, I thought it was an isolated incident... I guess not. what a major PITA!
To add insult to injury, I ordered the wrong size coupler lol. Now my machine is completely down until the correct size coupler comes.
Oh right ok, it is one of the set screws but has a socket cap head which i believe is an m3The grub screw or set screw is the one without a head on it. https://www.google.com/search?q=grub+screw