Bet you’ve never seen this sort of welding before. It’s called friction welding.

Technically, because no melt occurs, friction welding is not actually a welding process in the traditional sense, but a forging technique. However, due to the similarities between these techniques and traditional welding, the term has become common. Friction welding is used with metals and thermoplastics in a wide variety of aviation and automotive applications.

So very cool. Science! [h/t Daniel Mark]