I'm trying to replace a very old lockset on an exterior front door. It would be great if you all could help me figure out a replacement.

From what I know, I would guess this is a 2-1/2" or 2-3/4" mortise backset? I also know that the faceplate size is typically very important so they can fit into the existing mortise hole, otherwise it turns into far too much work. Left Handle vs Right Handle I see sometimes matters on the lockset since some of the old locksets had the lock on the bottom, where mine has it on the top.

Do replacements exist without breaking the bank? Seems like I'm seeing some in the $60-$100 range, then others in the $300+ range.

Possible Product 1: Segal SE 27580 2-1/2 In., Backset, Entrance Mortise Lockset, Wrought Solid Brass I would rather not gold/brass, but if its a direct replacement I would be fine with the color. The lock faceplate here is 1", I need to double check if that is the same.

Possible Product 2: 2.5 in. Satin Chrome Left Hand Entry Mortise Lock Set with Backset and 2 SC1 Keys The backplate looks very different from how it looks now, but again if a direct replacement would be fine with it. The lock faceplate here is 1-1/8" which may be too big.

Alternative Plan: If I can't find a replacement, I'll be forced to remove, fill with wood blocking and bondo, and cut an entire new door handle/lock, and strike, and would then simply buy a more modern setup. With the idea of a replacement mortise setup saving me a lot of time, I'd prefer that route. Otherwise, the alternative harder plan will be in place.

Any tips on what I'm looking for, and if either of those 2 possible products will work. Other tips or feedback appreciated.

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  • 1
    What's wrong with the old one?
    – popham
    Commented Nov 9, 2023 at 23:07
  • I was hoping to install a nice newer looking handle since this one is old and dingy. Also, a painter took it apart and put it back together and now its sort of funky the way it operates. Any idea if its missing 2 screws where those 2 empty holes are on the side plate? Assuming he lost some screws possibly. I suppose I could try to polish it, and take it apart again and try to reassemble it and see if it helps. A new option would be nice, at least so if this doesn't work out I can replace it with a mortise style. Otherwise I'll need to close it up and start again.
    – RocketManZ
    Commented Nov 9, 2023 at 23:25
  • 1
    Those two holes look drilled to me. If they were for screws, then there would be a taper from countersunk holes. The edge distance is all wrong for manufacturer's work, too.
    – popham
    Commented Nov 9, 2023 at 23:51
  • 1
    I guess I have a different attitude, but a block of wood glued into the old mortise hole doesn’t seem like a lot of work. You’d end up with a bit of bondo on the edge, but wouldn’t have to work too hard on the faces, as those would be covered by new. Commented Nov 10, 2023 at 4:12
  • 1
    @AloysiusDefenestrate Good point. 6 in 1, half dozen in the other. Blocking also means needing to rework the strike plate area, then possibly the wood stop to get a proper gasket seal, and before I know it I'm knee deep in an entire weekend project. So just testing my options on a more simple replacement before I rip it all out and block it up and start fresh. Digging around the web, I may be able to replace the lock cylinder since I do not have the key to this setup and possibly salvage it with a new handle. Learning far more than I imagined on these old mortise setups.
    – RocketManZ
    Commented Nov 10, 2023 at 15:44

1 Answer 1


Backset is distance from door edge to centerline of knob and lock cylinder.

Other dimensions of mortise locks may also differ depending on their age and manufacturer. If you really want to replace it, you want to dismount it, make all those measurements, and try to match them. A locksmith can check catalogs to see if they can get a match, or you can take a diagram and/or the old lock to a home center and see if they have anything in stock that matches. If those don't find a match, you may need to modify the door; "repair plates" are a standard way to hide the old holes that will look OK.

But if you just want to replace the knobs and the knob roses behind them, that can generally be done without replacing the lockset. Loosen the knob setscrew, and the knob will unscrew from the threaded shaft. Remove the screws holding the roses. Install new roses and their screws; install new knobs and tighten their setscrews. If the knobs seem to be rubbing, loosen the setscrew and back one or the other knob off a quarter turn; retighten and try again. If the knob fit is sloppy, reverse that and tighten a step or two at a time until you have the best compromise you can get. This should be cheaper and easier than replacing the whole lockset.

"Architectural recycling" stores may have used but good-looking knobs (and lock sets) at reasonable prices. Or your local locksmith may have some they rescued from past jobs. I have a nice pair of crystal knobs that I should swap into my library door one of these days.

  • Thanks for this info. Didn't think about just swapping the handle, good idea I've done this on interior doors so I'll see if I can find something compatible for this exterior setup. I also do not have the key so I need to find a compatible lock cylinder if I'm going to keep it. I've been digging around the web and am learning and awful lot about lock sets as a whole, so I may salvage this, or, block it and bore new holes with a common lock set.
    – RocketManZ
    Commented Nov 10, 2023 at 15:38

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