I have an antique glass door knob I am trying to remove. I have removed the screw at the base of the door knob and have tried to unscrew the door knob. It is stuck. I have tried spraying WD40 to loosen it up, but that didn't work. Don't care if I have to break the door knob. It is being replaced. Any help would be great. Thank you./
It is definitely a threaded connection. The threaded rod (spindle) looks something like this:
Now that the set screw is out, lean on it (especially if you don’t care if it breaks).