The left hand video, shows the bronze bar being machined to size. Here the part that will become the threaded section, is being turned to a diameter of 22mm, before being screw cut with the new thread. 

On the right, the hexagonal part of the plug is being made, the part set up on the rotary table, which makes the process straightforward.

Once the hexagonal part is completed, the piece is put back in the lathe, for the thread to be screw cut. This is shown below, and the finished plug fitted to the block.