David,
It is a piece of allthread rod that will screw down into the pin. I do not know the thread size right off the top of my head. The "nut" is a homemade nut made from a piece of key stock. The nut has to have more thread contact than a conventional nut of the appropriate size. The socket is obviously a deep socket sized there the pin can go up inside of it while it is being pulled out. Put a flat washer between the nut and the socket.

__________________
Jim