Problems drilling a socket

[chucketn]

I’m in the process of making a Drawbar wrench/Hammer combination tool from a deep socket, a brass plug for a hammer face and an aluminum handle. I parted off the square drive end of the socket to reveal a round center. I soldered in a brass head and faced it square and turned it to match the diameter of the socket. Then I put the socket /head in my mill vice, found center and started drilling for the handle. I used a center drill first and started step drilling to the tap dia. for ½-13 thread for the handle. The first step drill went fine; the second just squealed and did nothing.
I have since tried to use an end mill and various other drills to get through the socket wall. Nothing will now touch it! What happened? Did I work harden the socket? Is this salvageable?
Chuck