Principles of Bypass Keying

The bypass keying option with suite master is an impressive keying option. Offering bypass keying may seal the deal when selling a masterkey job.


Bypass keying, a masterkeying specialty, is a form of controlled cross keying, primarily used where there is an office suite with an external door and a number of offices within that suite. The front exterior door is operated by any of the interior door keys. This allows users to carry a minimum...


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See Chart 1 for a representation of the bitting list developed. Take a close look at the block and we will now start assigning the key codes to these bittings. I will always assign the first change as the individual code and bitting for the bypass cylinder itself, and only the bypass cylinder. This bitting is not to be applied to any other office or application other than the bypass cylinder. It is from my experience that it is always good to have a key only for bypasses, and not anything else. In some cases an employee may only need access to the suite and copy room and not to any offices. The key code assigned to this bypass can also become an identifier with an X behind it, denoting a bypass cylinder.

So to create the bitting list, I develop it from this block of the master key page. With all the bittings listed fully, I can get an overview and also account for maximum adjacent cut problems (MAC). MAC may eliminate some of the bitting off the list. In this case all 16 changes can be used.

Once all the bittings are listed, and they are usable, I start assigning the key codes to these bittings. In other words, cylinder AA1X will be operated by keys AA1 to AA16 and also by the suite (block) master, building or floor master (page master) and the top master (building or grandmaster).

On the bitting list a note is made by AA1-AA16. The X applies to the cylinder usually to identify it as a bypass. An “X” may or may not be applied to the key itself. Now with the bitting list fully developed, I can apply these key codes to the appropriate door. Of course the whole reason for this exercise was to create a bypass cylinder. So now is the time to apply these codes. Let me start with the bypass first.

Let me backtrack a little here. The first thing that should have been done in creating the key system of this facility was to sit down in a keying meeting with the owner or representative of either the facility or the end-user. Everything from sizing the masterkey system, type of system (grandmaster or not; existing system add-on or not), submasters, and of course the bypass, and where all these are to be applied, flows from this keying meeting. One should have a very clear idea of where the bypasses should be applied. So at this stage once the bypass is assigned its number and the X suffix, it gets assigned onto the floor plan, for the bypasses. Then depending on key alike groups or key different masterkeying, apply as appropriate using the codes according to the key plan. If building from scratch, it would be a good idea to assign the actual code to be used. That is why I am consistent with using the first code detailed as **1X as the bypass. Now it’s a matter of having a bitting to go with it. As stated before, this meeting will determine how many bittings to setup the bypass with and the overall size of this masterkey system.

If the first block that was chosen becomes the first bypass for the first suite, then a second block can be picked out of that page of the progression array and the same done; that could be the bypass for the second suite. It is from my experience that if an office suite exists, there usually is one across the hall too. So when keying an entire building, the second bypass will be important. Because it is from a different block, and that block master is the suite master, there is no possibility of one set of keys in suite A to operate suite B across the hall. Even though 99 percent of the keying is identical to each other, that 1 percent will keep suite A keys from operating suite B and vise versa.

A shortcut is to leave a stack chamber empty. This has its advantages and disadvantages to be determined by the application of the bypass. Of course having all the pin tumblers in the stack chamber provides more security than an empty one. If there are issues of the stack jamming due to worn keys or worn cylinders, and no one seems to want to replace their worn keys, it may be better to leave the chamber empty, especially if you determine that what the bypass cylinder is protecting is low security. As example: going into an empty main suite or conference room with only tables and chairs. If there is valuable equipment in either space, then that affects the decision to leave a chamber empty or not.

When customers are given bypass keying as an option, they are usually quite impressed. It cuts down on the number of keys carried, makes it simpler for the end user, and in some cases encourages the locking of certain doors that may otherwise be left unlocked.

A caveat: If the bypass itself needs to be rekeyed, selectively deactivating a key out of the bypass may be either difficult or impossible and involves a time consuming calculation. Other options to mitigate this caveat are to:

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