Fixing an antique doorknob and mortise latch set

By | May 22, 2012

Our house was built around 1886. It has never had a gut remodel, which means that much of what’s in the house is original, including most of the interior doors, doorknobs, and hardware.

Unfortunately, this means that a lot of the knobs no longer turn, or they turn but the latches don’t move, or the latches move but don’t latch, etc. One of our closet doors hasn’t latched properly since we moved in 15 years ago; since it was just a closet door, we didn’t bother to do anything about it, but when I went to open the door the other day and the knob came off in my hand, something clearly needed to be done.

The problem was that the screw which holds one knob onto the squared shaft protruding through the door from the other knob had mysteriously disappeared:

Incidents like this are not terribly uncommon in a house with a lot of kids. When an adult observes a loose screw, handle, or what-have-you, the normal reaction is, “I should fix that,” or, “I should save that part so that it can be fixed later.” When a child observes a loose screw, handle, or what-have-you, the normal reaction is, “Loose screw? What loose screw?” or worse, “Ooh, look, a new toy!” I’ve lost count of the number of times I’ve had to improvise repairs because by the time it came to my attention that something was broken, its original parts were long gone, having been appropriated as toys and then lost by the children.

So my first problem was that doorknobs like this require a very specific kind of machine screw (relatively thick compared to its length), and the screw was long gone. Perhaps I could have found an adequate replacement at a good hardware store, but there was a faster solution… When we moved into the house, we took down a couple of doors to make the floor-plan more open, and stored them in the basement. So now instead of a closet door with a missing screw, there is a door in our basement with one. The next owner of the house can deal with finding a replacement. 🙂

So I reattached the knob:

But since I was already working on the door, I couldn’t resist exploring a little bit to try to figure out why the latch wasn’t working and whether I could fix it.

Unfortunately, I forgot to take a photo right at the beginning, but this is basically what the side of the door looked like before I started working on it:

The only differences, whose reasons will become obvious later, were (a) less of the paint was scraped off at the start of the project, and (b) the latch was stuck inside the faceplate instead of protruding as you see above.

Speaking of paint, let me take a moment to express wrath and indignation at every house-painter in the world who thinks it’s OK to paint over door hardware. You’re all idiots, you know that? Sheesh.

Anyway, I unscrewed and removed the knob I had just fixed, then removed the other knob by pulling the shaft straight out of the door. Then I removed the mortise faceplate:

and removed the hardware from the mortise, leaving it empty:

 Here’s what the hardware looks like when removed from the mortise:

The first problem I noticed was the aforementioned paint gunking everything up. Paint on the faceplate, particularly on the edges of the latch hole, and paint on the latch itself, were preventing the latch from being able to slide in and out as it needs to. So I scraped off a bunch of paint, and finally the latch was able to move freely.

However, even after doing that, there was no tension on the knobs, and the latch wasn’t springing out when the knobs were released. “Springing” is, of course, a most appropriate choice of words. I’m no locksmith, but even I knew there must be a spring inside the lock-set that somehow pushes out the latch when the knobs are released, and it wasn’t working for some reason. Next step: Take apart the lock-set and see what’s inside!

I should mention that the photos of the lock-set above and below were taken after I fixed it, not before, so you can’t see directly what was broken, but I’ll explain. Here’s the interesting half of the lock-set:

The reason why the spring action wasn’t working is because the piece of spring steel that’s supposed to provide it had worked its way out of position. Here’s a close-up showing it after I put it back into the right place:

And here’s the mechanism that controls the latch:

This is a simple, yet clever mechanism. The knob shaft fits through the square hole in the middle of the mechanism. When the shaft (i.e., the knobs) turn one way, the protrusion marked “A” on the part turned by the shaft pushes against the latch lever, causing it to retract the latch. When the shaft turns the other way, the protrusion marked “B” does the same thing. In either case, when the knob is released, the spring forces the lever back into its original position, and the latch springs back out again.

After fixing the spring and putting the other parts back into place, I closed up the lock-set, screwed it back together, put the faceplate back on it (making sure that the latch was protruding through the hole in the faceplate!), put the whole thing back into the mortise, screwed the faceplate on, and reinstalled the doorknobs. Then I tried turning the knobs a few times, when suddendly, sproing! I heard the spring pop out of place again, and once again the latch was stuck inside the faceplate. *sigh* So I took it all apart again in my work room and tried to figure out what was going on. Here’s my best guess:

I think what’s going on is that each time the latch is opened and the lever pushes against the spring (blue arrow), the spring creeps up slightly at the other end (red arrow), until it’s up far enough that it pops out of position and the lever is no longer spring-loaded. There are some protrusions in both sides of the case intended to hold the spring in place, but they aren’t good enough.

Well, that’s easy enough to fix, right?

The two notches in the block leave room for the case protrusions which are (supposed to) hold the spring in place. Here’s what it looks like closed up:

Et voilà! A working latch:

Well, at least, I hope it’s a working latch. Only time will tell how good my solution to the popping spring is!

A few more notes about this project that are worth mentioning…

To make the latch more secure, I wanted to decrease the gap between the latch and the latch plate in the door frame. My first idea for doing this was to put some washers on the two latch plate screws between the frame and the latch  plate, to hold the latch plate away from the frame. When I tried this, I discovered that the wood around the screw holes in the frame was pretty beat up, such that the screws really wouldn’t grip well when I tried to put them back with the washers. So I tried filling in the gaps with wood filler and letting it dry for a few hours before trying to screw the latch plate back in:

But when I then reinstalled the latch plate with washers behind it, the door wouldn’t latch, because the latch plate was just a little too far back, so when the door was all the way closed, the latch wasn’t quite past the front edge of the latch plate.

Given that I was going to have to move the latch plate anyway, I decided to go all out. Not only did I fill in the holes in the wood filler which I’d created in my first attempt, I also put on a lot more filler:

This was necessary because to move the latch plate forward enough, I was going to have to move it out of the indentation chipped into the door frame for it, so to make the latch plate level, I had to fill in part of that indentation with filler. I used the latch plate as a template to draw the circles you see in the photo above; they show where I’m about to drill starter holes before screwing in the latch plate, this time without washers, since they’re no longer needed now that the desired depth has been achieved with filler.

I ran into two other problems with “screws that wouldn’t screw”: one of the screws holding in the faceplate was loose because the wood behind it was chewed up, and the screw that holds the lock-set closed had also worn out over time and was refusing to hold the lock-set tightly. I solved both of these problems by filling the holes with steel wool before reinserting the screws.

I don’t know whether the lock in this lock-set actually works, and I didn’t bother to do anything to find out or repair it, because the keys for all the interior locks in our house were all lost long before we moved in. Since we don’t use the locks, it wasn’t worth doing anything about this one.

 

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7 thoughts on “Fixing an antique doorknob and mortise latch set

  1. Sheila

    Please help! the spring lever in mine is broken. How can I get a replacement part? Anyone??

    Reply
  2. Ken George

    I’ve got bearing parts that have prongs that go under the rosette. Some have 3 and some have 4 prongs. They press into the door and the rosette holds them in place. It reduces wobble of the shaft and knobs. Do you know where I could source some of these?

    Reply
  3. Tanya

    Thank you from the bottom of my heart. And painters need to see the error of their ways by gads, I was nearly crazy trying to get the screwes cleaned off enough to get to the true issue. I am happy to of fixed the lovely old door then have to replace it with something of less character.

    Reply
  4. TJB

    Thanks for the info and great pics. I fixed 4 mortise latch and door knobs with the info here. Taking ‘before’ pictures helped out a lot, as did having one mortise latch that was intact and functional to use as a template once I removed the paint that was gumming things up. I had a couple of snapped leaf springs and had to replace them. The only place I could find the spring steel to make the spring was at my local locksmith (and they didn’t really seem to want to sell me any). It looks like the spring steel can be purchased online (HPC spring steel assortment), but it is spendy and seems a bit ridiculous to buy several pounds of spring steel when you only need one 5cm strip.

    Reply
  5. Gary

    Interesting. FYI, a common fix for a wood screw that has chewed out it’s hole is to stick a toothpick or two in the hole, and break them off after setting the screw.

    Reply
    1. jik Post author

      Yes, I know about filling in screw holes with toothpicks. I find it’s better to pack them in as tightly as possible, dip them in glue before doing that, wait for the glue to dry, and then cut off the protruding ends with a hand saw or even wire clippers before putting in the screw.

      Having said that, steel wool also works in some cases when the hole isn’t completely beyond redemption, as was the case here with the faceplate screw hole, and it’s a lot faster and easier than the toothpick method.

      As for the latch-plate holes, toothpicks would have worked for one of them, but the other one was way beyond that, and since I was going to the trouble to fill in one of the holes with filler, there was no harm in doing the other hole that way as well.

      Reply
  6. E.T.

    Great project! I’m glad that what started as an annoyance turned out to be potentially useful.

    Reply

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