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?
With copper, brazing and/or soldering was used, depending on the joint being joined and the manufacturer.
I don’t know how it’s done these days. With plastic tanks and aluminum now used, I can only guess that bonding agents are applied.
I believe the two parts are just drop forged and riveted together.
I spent four months working in a hotel type air heating and cooling equipment factory. Never worked on the radiator line but they had machines that just press on the sheet metal fins onto the copper tubes. Then we just put it all together with the valves and motor, etc. I love watching how stuff is made. Not the TV show.
I sort of guessed already that the top of the cylinder must splay out a bit, and that’s what prevents the two pieces from coming apart. But how do they press the parts together then? Or are you saying when the hole is drilled in the one piece , the top of the hole is a little wider? Like if you were making a hole in a piece of wood for a wood screw that you wanted to sit flush to the surface. And the cylinder isn’t splayed out when the parts are put together. Then a hammer or something whacks it, which splay it out to fit the top of the hole, sort of like a rivet?
Reference the picture with the thru hole and chamfered finish to the hole on each plier piece. The chamfer allows he rivet to be hammered so the head expands into the taper without swelling the middle too much. If just the rivet were hot when that is done, the metal would flow more easily and once cool the center would shrink down allowing the pliers to open and close. Finish grind both sides and you have a pair of pliers. That’s my best guess.
That is how every rivet in the world works . A rivet is put through a hole with a head that stops the rivet from falling right through then the other end is expanded by mechanical or hydraulic means.
But a proper rivet is tight in the hole after peening over. That won’t work for pliers that have to move so its not quite a proper rivet. So, how is the slip fit maintained?
Yes, that’s my question also. If you look at the finished product closely, there is no noticeable gap, just a fine line, too thin for me to even guess at it’s width.
Oh, so they start with each piece having a hole in it? I was thinking one of the pieces had a chamfered hole, and the other piece just was made with a built-in cylinder sticking up that goes through the hole. No third piece, the rivet. B/c I can’t see any signs of a rivet there on the non-rotating-joint side. But yes, the video is pretty clear the heated and bashed rivet fills the chamfered part of the hole. And that mushrooming effect prevents the two parts from separating. As mentioned already, while it’s easy to see how the rivet could be dimensioned a little smaller than the hole to provide clearance for rotation, harder to figure out why the mushroomed part doesn’t bind. But I guess they figure that out by trial and error, depends on how hard you bash the rivet.
I’ll take another look at my pliers, see if I can see signs of a rivet on the other side. I guess it could be done either way, but the rivet method seems like it would be easier. Anyway, thanks for the interesting comments. I’ve gained a little more understanding at least. It’s amazing what can be done if you have a machine that heats stuff up enough and can bash the parts into a mold with enough force! If I had to do that in my driveway I’d be looking at a 2 year experimental process, and I’d be lucky, if I could accomplish it in that time … lol …
