Tuesday, June 18, 2024
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Learn to Understand and Interact with the Mortise Lock

When the house that you live in has a rich history, there are almost certainly some fun (if delightfully mundane) secrets to be found. Among them is one that you may interact with daily … the mortise lock! The term “mortise” in joinery and locks refers to a slot cut or carved into a piece of material to fit a different object with as little wiggle room as possible, effectively joining them together.

There are three steps in figuring out whether there is a mortise lock in any given door without disassembling the door itself. The first is to get an approximate knowledge of the house’s construction date. In addition, one can check the deadbolt and doorknob to see if both are flush with the same plate on one side of the door, and look to see if there is a decorative rectangular-shape protrusion around the doorknob with a classic keyhole shape cut into the metal. Any of these may indicate that the lock in question is in fact a mortise lock.

The process for typical restoration is fairly simple. One loosens the bolt from the base of one of the door knobs, removes the knob on both sides with the spindle still attached to the obverse side knob. A knife will be needed to slice around the edge of the side plate if the door plate has been painted over or otherwise covered. In addition, paint that is in the screw threads should be removed. After this, one removes the screws from the side plate leaving only the wood of the door to support the lock assembly, carefully removing the assembly without damaging the door or side plate. I recommend carefully prying the lock out of the door with a flat head screwdriver and pushing from the hole left from the removed doorknob. 

After the lock is removed, unscrew the bolt from the center of the face plate to see the specific lock model. Depending on the determined type, one will vary in next steps. If the insides seem lined up, take a photo of the set-up; otherwise one will use mortise example images found online. Using a rag and some water or cleaning solution, thoroughly clean each part. If the pieces are rusted, use a vinegar or lemon juice bath to weaken or remove it. Leaving the components to soak overnight outside or in a well-ventilated area tends to get rid of most of the corrosion. 

After this, gather steel-wool, a small brush, rags, and a container with baking soda dissolved in water to neutralize the acid. Wipe off the vinegar solution and drop the cleaned pieces into the baking powder solution. Clean off any oxidation with the steel wool and brush. Wipe the pieces thoroughly and coat them with machine/bike grease to prevent rust and allow for better movement. Reassemble the lock, and either reinsert it or take the rig to a locksmith and cut skeleton keys, the cost depending on how many of your locks you want the keys to affect. All that’s left to do is reverse the extraction process to get the assembly in and the door functioning again. Now you can lock it and say “I did that.”


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