@finnian3: see this image for various pipe parts.
The "Tenon" #6 in the picture above has a screw-in fitment on most Kaywoodie pipes. #5 is the Shank mortise and on Kaywoodies, it is a aluminum insert that screws into the shank and received the threaded stem. Generally speaking, most of this metal work was aluminum or perhaps pot metal.
The end of the threaded piece,typically with a ball, is known as the "stinger" in pipe terminology.
You can read about many types of pipe restorations at the Reborn Pipes blog, the link shown in my first post. I, and several other restorers post our work at that site, which is owned by Steve Laug. He also has a blog entry there on the different kind of "stingers" used by various pipe makers. Stingers were meant to stop condensation from coming back thru the pipe stem. In those days, makers were always looking for a gimmick to provide a "dry smoke". Kaywoodie stingers were patented with the "Drinkless" name.