I am wondering how the screw top of a container made of either aluminium or brass is manufactured at scale. A picture of the sort of thing I am talking about is below. Currently the only method I can think of is hydroforming. Can anyone enlighten me?
These threads are rolled. The blank is automatically fed to sit around a central wheel which has the form of the thread. An external arm with the opposing half of the form then lowers to apply pressure and form the threads, before being automatically ejected from the central wheel, ready for the next part.
This video https://www.youtube.com/watch?v=HykVRyTsV20 shows a machine forming the threads on a cap, but the process is identical for the container itself.