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I Forge Iron

Spinning a Rivet on Purpose


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I'm aspiring to repair an old broken rim lock in our house. The internal part that turns when one twists the doorknob has broken in two:


That lever is supposed to be attached to the hub at the arrow. Here's what the part looks like in a good lock:


The part is firmly fixed to the lock's base plate, although it rotates - there are no other parts holding it in place. On the outside of the lock you just see a rotating ring, flush with the face of the lock:


Dissection was required. I cut the broken hub in half to figure out what held it in. Turns out it's a glorified rivet:


The hole in the lock base plate is chamfered: it's 0.5 inches on the inside and 0.6 inches on the outside. Obviously the half-inch part was inserted, peened to the shape of the chamfer, then ground flat. I haven't done this before, but probably can figure it out.

But the question remains: How do I make sure the riveting job rotates when I'm finished with it? It does me no good if I peen it so tightly you can't turn the doorknob...

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  Does the rivet ride in a groove in the rotating ring to hold it all together?  Is it a lock or a door latch?  Im not an expert on such things but I keep looking at it and just get more confused.

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If the hole and chamfer in the lock base are nicely centered and round, I would try treating it like loosening a rivet on tongs. Peen the rivet over hot with while the lock base is cool. That way you don’t deform the hole or chamfer, then quickly work around with a square “key,” and if doesn’t free up, heat the whole thing and try again. Of course I’m assuming none of this is cast iron. (Oh yeah, use lightest hammer that seems to work. You only want to move the material on the top.)

Just my thoughts, maybe others will jump in...


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>> Is it a lock or a door latch? <<

The overall mechanism is both. The part in question belongs to the latch side of the contraption. Doorknobs are attached to a square shaft which passes through the middle of the part. The part's arms push on the actual latch to move it.

>> Does the rivet ride in a groove in the rotating ring to hold it all together? <<

The part itself is the "rivet". It protrudes into a chamfered hole. The narrow side of the hole is on the inside, it's wider on the outside. The part has been smashed to match the chamfer, which holds the part in place in the lock.

>> I would try treating it like loosening a rivet on tongs. <<

Thanks, good suggestion. All other suggestions are welcome. I'm going to try experimentation on surrogate set-ups before I bugger up a 90-year old lock!

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There is a circular indentation around the edge of the rivet end.  I would guess some sort of rivet header was used. Maybe one with a square tenon to fit the square hole to keep from deforming it when struck and to be used as a handle to free the rivet so it spins? 

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  • 3 weeks later...

BillyBones, sorry I missed your post. You're probably on the right track.

I decided experimenting on something other than the real lock might be bright idea. Steel cover plates for electrical boxes are the right thickness, so I drilled and chamfered holes in a few. The stunt double for the lock part was some 3/4-inch rod on which I turned a 1/2-inch end and drilled end-to-end the same size as the doorknob shaft hole.

Then I started hammering. Peening worked, but it was pretty ugly. What worked best was a mandrel with a short taper to expand the "rivet" from the inside. It's the mandrel on the left:


Crafting the part involved a bit of cutting, turning, broaching and filing, but no hammers. Sorry.


So the part goes in the lock shell, poking through its hole. A piece of bar acts as a backing plate as there are other parts attached to the shell that need to clear the anvil. A block of wood with a hole keeps the mandrel vertically aligned. And bungee cords keep the whole assembly from wandering around the shop. (I knew I put those chains around the anvil for a reason!)


A single, healthy wack with a 3-pound hammer did the trick:


Here's the flip side with the latch parts in place:


The whole thing is back together now and on the door. Whew!

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I to am doing some work on doors and locks. Here is one that i just got through cleaning up and ready to re-install. This one goes into a pocket in the door. The striker plate and lockplates for the doors have that same pattern on them.  


I also have the style you have through out the house. Fortunately those were not painted over. 

Anyway just thought you would like to see it. Also i do not think this one is as old as yours having the stamped steel body and all. I am also pretty sure that the pattern was stamped then chased by hand. You can see small inconstancies from one to the other but, in my opinion, they are to uniform to have been done completely by hand. 


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