trying to remove a screw on type jack

[Ron Victoria]

I am trying to fix an old lap that has the screw on type of jack. Looking side the guitar, there is a brass barrel with the ground soldered on. The center lead has come out of the barrel. The length of the entire jack counting the barrel is maybe 2 inches. I thought the jack would just slide out, but now I see something metal, maybe a pin of some sort that holds the barrel in place. It's smooth and round. I'm thinking to try and drill and see where that goes. Maybe the metal I see is just a cap and there's a screw underneath. What about if I protect the threads on the jack and see if it moves? I'm open to suggestions. I teach metalshop so I'm a veteran. Thanks, Ron