God forbid the dark day comes when your building’s master key is compromised. Perhaps it was forgotten in a lock, carelessly left on a desk, or was in a stolen purse. However it was lost, somebody has it and they may mean to use it to commit some crime. Hopefully only petty theft, but possibly assault could occur and you might be held liable. But you already know that or you wouldn’t be reading this!
The obvious thing to do aside from getting the master key back from the criminal is to change the master key to a new key without changing any of the tenant keys. Easier said than done! It is possible to do easily in some circumstances, but it may make sense if the tenant keys can’t be changed to deactivate the master key for the building until a later date. Read on for details…
Let’s start off with the perfect scenario (if one forgets about the highly imperfect start to this scenario), where a building uses a master key system that was designed with one or two chambers held constant for tenant keys but the master key is different for that chamber. In this scenario all the locksmith has to do is cut a new key to be designated the master with a different depth that the previous one for that chamber, and change the pins for that chamber. The old master key won’t work for any lock that this is done for.
In my experience this is not likely for most buildings where different locksmiths have come in and rekeyed the locks to work with the master key but haven’t adhered to any system for the building. It is possible there never was a system, or the system was drawn up on a napkin forty years ago and immediately used to blow one’s nose and thrown away. This is one of the times when it becomes obvious why it is great to have and maintain a proper master key system. Following is a more technical explanation for why this is difficult if there was not a chamber held.
Successful masterkeying requires paying attention to many details. Different lock manufacturers have different specifications for what pins can be used in their locks. Some locks, like those manufactured by Sargent, are machined to such tight tolerances that you can use master pins only .020″ thick. These are thin little round pieces of brass that enable one more key to work for each one. Add two of these in a pin stack and you can have two more keys work in that lock cylinder. If you put that same .020″ pin in a Schlage or even worse Kwikset cylinder it will jam up. Not immediately for the Schlage but eventually it will. It will happen almost immediately for the Kwikset lock which typically have very loose tolerances.
In a master key system there are many more rules and limitations based on the angle of the cuts on the key and other boring things I will leave out because I’m not trying to write a book but suffice it to say that if you have a building with say twenty units and everybody’s lock is using the same pins on the first chamber, you can make a new master key work in that chamber but you can’t make the old master key stop working for that chamber because everybody else’s key has the same cut as the master key for that chamber.
Another problem that prevents easily changing the master key is if tenant keys are differing by depths of something other than a standard depth. Master key systems cannot work properly if there are keys that are cut too closely to the master key. Schlage master key systems are supposed to work in increments of .015″, for example, but a master pin can not be less than .030″. If you have a system that isn’t really a system but actually just a hodgepodge of keys that are compatible but not in a system it becomes somewhat difficult to change the master key because in the second chamber all of the tenant keys may be .030″ different from the original master key but all other possible cuts for the master key could be .015″ difference.
To make it even more complicated, if we are being responsible human beings we must consider whether or not the master key might work in these locks even after changing the pins by pulling it out slightly. I subcontracted for another locksmith who controlled the restricted keyway for a customer I was doing this very thing for, we were changing the master key without changing the tenant keys. The new master key that they chose had different depths but unfortunately if you pulled the old master key out a little bit in the locks keyed for the new master key it lifted the pins to the right height. This was partially because some doofus in the past filed some of the plugs which made the cylinders have looser tolerances.
Assuming that your building is like many apartment buildings in Seattle you probably have a hodgepodge of keys not conforming to an actual system. The best I can do for you is measure the depths of all of your keys, make a matrix, and from that figure out the least invasive way to change the master key. It may be possible in a small building to choose a new master key without impacting anybody else. It may be required to change one tenant’s keys in order to keep the master key from working.
I know that this is probably an impenetrable mental puddle of barf to anybody but me or maybe another locksmith or at best a lock enthusiast but hopefully the takeaway is that master key systems depend on rules about how compatible keys are cut and if the tenant keys aren’t all created based on a sensible system like rolling constant, the chances of changing your master key in an existing system without changing at least a few tenant keys can be unlikely.
