I’m in the process of removing the York AC compressor for rebuild. I’ve spotted a fastener that I do not understand. It’s a 22mm hex nut threaded onto a stud which has an Allen cap screw in the center. Never seen anything like this before and want to be sure if I remove the 22mm nut I don’t end up with a problem. Camera didn’t want to focus on it, but it’s dead center of the attached photo.
Any advise/experience?
TIA
Matt
ETA: Added a slightly sharper photo.

