How to Rekey a Mortise Lock

What You'll Need
Mortise lock cylinder
What You'll Need
Mortise lock cylinder

A mortise lock is a type of locking device that is made up of a large rectangular body that fits into a mortise shaped in an edge of a door. The whole locking mechanism is housed inside the lock itself, which includes mechanisms for the knob, deadbolt and latch. Mortise locks will take a standard key like other locks, but it is designed to be rekeyed over and over again. Rekeying is a process wherein you want to keep the lock system but would like to use a new set of keys for it. Here is a way to rekey your mortise locks. Keep in mind that rekeying will require you to change the cylinder of the mortise lock system.

Step 1 – Check Keyway Positing

Open the door where your mortise lock system is. Remove the cover plate that houses your mortise cylinder with a screwdriver. There will be two screws that you need to remove. Set them aside because you will need to replace this again later after you have replaced the cylinder. Remember the keyway’s position inside the cylinder. Usually, the keyway will be positioned at the bottom of the cylinder.

Step 2 – Remove Cover Plate

Remove the cover plate. Unscrew the screws that hold the mortise lock cylinder in place. If the mortise system has an inner and outer cylinder, there will be more than two screws.

Step 3 – Remove Mortise Lock Cylinder

Remove the mortise lock cylinder. Turn the mortise lock in a counterclockwise manner. Take your new mortise lock cylinder and turn it clockwise. It is important not to counter-thread the new cylinder, as this can damage the mortise lock mechanism of the cylinder.

Step 4 – Line up Mortise Lock Cylinders

Line up the mortise lock cylinders properly. Remember that if the keyway is positioned at the bottom, this is how your new cylinder should look like as well. Tighten the screws to the cylinder.

Step 5 – Test the New Mortise Lock System

This will ensure that you have placed the new mortise lock cylinder properly. If not, turn the mortise lock cylinder just one turn the other way around in a counterclockwise position, but still making sure that the keyway will still be positioned at the bottom. There will be times that this will still not work. To resolve this issue, trim rings will help the mortise cylinder fit better.

Step 6 – Replace Cover Plate

Once the mortise lock system has a new cylinder so that a new set of keys can be used, screw back the cover plate and make sure it is done tightly. Prior to closing the door and locking it, make sure that you test it once again while the door is ajar. This will ensure that you have properly rekeyed your mortise lock system.