Replacing A Mortise Lock

One most often finds mortise locks in aging homes. If you’re aren’t familiar with the name, these are the locks that have a door knob with a key hole underneath, separated by the wood of the door. They are most often seen in houses built before the 1970s. There are upgrade kits available for these to modernize your home, or you can simply replace any broken or old locks with the following 6 easy steps.

Step 1: Test the Locks

Figure out first which door needs to be fixed by testing out the locks on each of them. Open the door that you want to change the lock cylinder on. You’ll see that on the narrow part of the door, there is a plate that goes over the lock cylinder. Remove the screws that are holding this plate on, and make sure that you put them in an area that won’t get disturbed during the next steps. Make sure you pay attention to the position of the keyway in the cylinder, which can most often be found at the lower end of the mortise lock cylinder.

Step 2: Remove the Plate

Once the screws are removed, remove the plate and remove the screw that keeps the locks cylinder in place. Depending on the type of mortise lock that you have, this may just be one or it could be multiple screws (remove them all). You may also find some mortise locks have more than one cylinder, which again is okay, just remove them all.

Step 3: Remove the Cylinder

Remove the cylinder from the lock simply by turning it in a counter clockwise fashion like you would do a screw. Take care on particularly old doors not to damage the wood frame as you remove the lock (as old doors can sometimes be susceptible to damage on non-painted surfaces). Place it to the side for later discarding, and insert the new cylinder by turning it in clockwise (again, like a screw). Take caution not to counter-thread the new cylinder, or it will cause a problem with the security of the lock.

Step 4: Line Everything Up

Make sure that the new mortise lock cylinder lines up correctly with the keyway. Remember that for most mortise locks this will be at the bottom, but it could be different for yours. Now take the set screws that came with your new mortise lock and inset them and tighten them.

Step 5: Test the Lock Again

This is the time that you want to test whether or not you have successfully placed the new assembly in the right places by checking to see if the lock works properly. If it doesn’t, then you’ll need to rotate the mortise lock cylinder once counter clockwise to get a different fit. If that still doesn’t work, then you can try some trim rings from your local hardware store (but you might be better off looking into a new lock).

Step 6: Replace Cover Plate

When you find that the locking mechanism is working to your satisfaction, then simply place the cover plate back on and fasten it with the screws that you so carefully placed aside earlier.