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Monday, June 30, 2014

Making a Key for an English Lever Lock

Every Time I restore a chest of drawers or cabinet that has locks, I take the locks out of the piece, clean them, and, if no key is present, I cut a new key that works the lock. After I cut the new key, I always think to myself "I should have taken pictures of how I did that!". So this time, I did.

The lock in question was a lock out of an English armoire I have been restoring. The piece was signed and dated October 11th, 1902, so I know that the lock is about one hundred years old. The type of lock is called a lever lock, which I will describe below. If you are interested in learning a bit about antique locks, take a look at this article on them:

http://www.worthpoint.com/blog-entry/keys-to-antique-furniture-locks

One of the most important things to have when you are making keys for locks is a large stockpile of keys of various shapes and sizes. I collect old 19th and 20th century keys that can often be re-cut to work a lock. I also have several new keys which look old and are uncut, giving me the widest range of possible cuts to make in the key.

Below is a photo of the lever lock, with the key I chose to work with to the right. This is a reproduction Barrel key that I chose because the outer diameter of the key shaft fit the hole in  the lock case and the blade was a little too long, giving me plenty to work with. A barrel key is one where the end of the shaft is bored out so that it can fit over a post in the lock.
The very first step is to remove the lock housing from the lock. This is held to the lock with two metal tangs that fit into mortices in the lock plate, which are peened over. By hitting the ends of these tangs with a screw driver you can release the housing from the lock plate, revealing the mechanism within. This second photo shows the lock with the housing removed.
As stated above, this lock is known as a lever lock. What this means is that besides the bolt which is moved by the key to engage the lock, there is a gate known as a lever that is also moved so that the bolt can be engaged. As the key turns in a lock, the blade length has to be right to engage the bolt as it swings around. The blade length needed to move the lever is different, so a second cut is needed to move the lever simultaneously. A tab of brass is attached to the bolt that moves with it, and passes through a window cut out of the lever. The cut on the key must move the lever enough to move this tab from one side of that window to the next and over a little ridge. This is also what keeps the lock in an open or closed position. Too much of a cut on the key will not push the lever into position for this to happen. Too little of a cut will make the lever move past the position it needs to be in.  Sometimes their can be up to three levers all requiring different cuts on the key, making this a tricky lock. This lock had one lever, so it was relatively simple to work on.  One other thing I might add is that the lever also has the spring attached to it which provides tension for the lock. If one were to try to remove the lever (making life simpler), the lock would not work. Below is a photo of the lever removed from the lock. we will get back to that later.
After the lever is removed, it is important to make sure that the key can pass through the lock housing and that the blade is long enough to engage the bolt and throw the lock. The key I chose fit all of the criteria with the exception that the blade was a little long. This is a good thing, because it is easy to file off the excess metal. The trick is to not file off too much metal, or the key will not work the lock and you need a new key. The photo below shows two keys from the same batch. The one on the left is the one that I cut for this lock. if you look at the blades, you can see that the one on the left is a bit shorter.
Below is a photo of the lock plate and the bolt. You can see in the lock plate where the previous key has left circular scratches from being turned over and over again. In this photo the bolt is in the thrown position.
Once the key blade was cut to the right length, it turns on the post and engages the bolt, moving the bolt back and forth from locked to unlocked position. In addition to making the blade the right length, it is sometimes important to round the corners of the blade so it engages the bolt smoothly. The next three photos are of the key working the bolt.


Once this was accomplished, I brought the lever back into the equation. Upon doing this I realized that the key blade and shaft was not touching the lock plate. While not critical, this could potentially interfere with the lock working properly and put unnecessary strain on the post, so the answer was to bore out the hole in the end of the key a bit so the key sat firmly on the lock plate when it was fully pushed into the lock. This also is important for alignment with the various components in the lock, including the lock housing. Below is a photo of the key before. you can see that the key is sitting high and off of the lock plate.
In this photo, the key has been bored out and the key is resting on the lock plate.
After this was accomplished, the second cut was made to operate the lever. This is seen in the photo below as a notch taken out of the lower right corner of the key blade. If you find an old key with notches taken out of the bottom edge of the key, that key was originally used to operate a lever lock.
The next few photos show the key operating the lock with the lever in place. The spring (which looks like a bobby pin) is seen to the right of the key going off at a diagonal. This would be compressed against the side of the lock housing and keep the lever under tension.



Once it was determined that all of the cuts and key adjustments were working I oiled the parts and put the lock housing back in place, putting the lever under tension. I then tried the key which operated the lock successfully. This can be seen in the last two photos below.

It is slow and fine work, but as long as a lock is in good shape, a new key can be made for it and it can operate successfully. One word of caution. If you are trying this yourself, make sure that if multiple locks are going to be using the same key, that you try the key in each lock to make sure it works. sometimes the key needs to be further adjusted for multiple locks and often, a lock will have been replaced, that will use a separate key entirely. Also, make sure the key locks and unlocks the lock successfully with the door or drawer not in the case. This way, the lock can be removed and the key adjusted. The worst case scenario is that the key throws the lock, but does not unlock it,and you have done this in the case, so the lock is locked and cannot be unlocked easily!

In the time that this furniture was made, it was important to be able to lock a piece of furniture that housed your personal belongings. In the 18th century, houses did not often have locks, and it would be an important security measure to keep you chests and wardrobes locked up. In today's world, this is not a necessity, but I feel that it is an important part of the restoration of the piece I am working on. If it is possible to get a lock (or locks) working again I will make sure they operate well.

5 comments:

  1. I appreciated your post and I am glad to read your ideas. Locksmith do a lot more than helping people get back into their locked homes or car. Thanks for the information.

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  2. Great, informative article. Thanks for sharing your knowledge

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  3. Very useful. I have a 4 lever drawer lock I am about the cut a replacement key for and you've provided some great insight. Thanks

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  4. I had a similar situation, but I didn’t have the fortitude to make my own key like you did. Thankfully, I have a locksmith in my area that has been there forever. They’ve seen it all. I swear, the guy that made the key for my lock might have been as old as the lock itself.

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