This is something I’ve been curious about and never figured out yet. Pressed together parts are a common thing w/automobiles, so maybe some of the experts here know the answer. I’ve got a pair of long nose pliers w/a similar design as the photo below. Two pieces, one w/a circular cross section hole, and the other with a cylinder part that just fits the hole. to connect the two it seems like they must be pressed together. Ok, that makes sense. But how do they make the two pieces then easy to rotate w/respect to each other, while not easy for the two pieces to come apart in your hands while using them?
This is the best photo I could find. Look carefully, you can see a faint line for a round inside circle where the rotation action happens, which is the end view of cylinder part. How do they make it so it rotates easily, but doesn’t just as easily come apart?