Articles about masterkeying have appeared dozens of times in Locksmith Ledger. Masterkeying has been the topic of books by well-known people in our industry. Full one or two day classes on masterkeying are regularly presented at almost every locksmith convention. With this background, what could possibly be new or different about masterkeying that has not already been discussed?
Cross keying and selective master keys reduce the numbers further. Master ring cylinders, on the other hand, use totally different rules and yield much larger systems. If you are planning a new system and find that the expansion numbers are a ‘close fit’ for one or more levels of keying, check with the Corbin Russwin Key Systems Department. How to have one master key for all your doors in your complex this will be done with minimal tools using several items found in your own home example a walgr.
What will be presented here is what might be called 'plug-in' masterkeying. It is designed to streamline the dull repetitive process of generating numbers and quickly move you into the profitable part of your job which is key cutting and rekeying.
First, a short primer on key bitting arrays. Yale set the general size for pin tumbler keys 150 years ago. Given this size, it was discovered that the Yale key size allows approximately 10 steps, or increments of depth from the highest possible cut on the key to the lowest possible cut. Lock companies may differ on what the dimension of each depth increment may be (usually between .0125' and .019') but regardless of the dimension being used, the amount of different possible increments for most popular lock companies is 10.
Most popular lock systems use five pin chambers for keying. Some commercial systems may use six or seven pin chambers, but this article will concentrate on a five chamber key system.
Variables such as parts wear and mass production can provide unplanned tolerances in a lock cylinder. With enough tolerance, key cuts such as 13131 and 14141 may unintentionally operate the same cylinder. This is called key interchange and must be avoided. In order to avoid interchanges, masterkey systems are designed to use a larger dimension of two increments between key cuts. Therefore in a masterkey system using key cuts such as 13131 and 15151, cuts of 14141 would not be used at all in order to prevent interchanges. .
Most popular keying systems use a depth numbering system of either 0-9 or 1-10. Since single increment steps should be avoided when masterkeying most lock brands, cut choices in a given chamber will be either 02468 or 13579. Note that the two choice groups are all even numbers or all odd numbers.
One of the key cuts in each chamber will be set aside for the master key cut. This leaves four choices of cut numbers per chamber for individual key combinations in the system which are called change key combinations. Due to four cut choices per chamber, this masterkeying system has become known as the quadrant system.
In order to use this plug-in masterkey system, you must know the cut numbering used by the lock system you are rekeying. As example, Schlage uses a numbering system of 0-9. '0' is the shallowest cut and '9' is the deepest cut. Sargent sectional keyways use a 1-10 numbering system. '1' is the shallowest cut and '0' (10) is the deepest cut.
Knowing the numbering system is important because not all cut combinations can be used due to maximum adjacent cut (MAC) problems. When a very deep cut is made next to a very shallow cut, the 'V' shaped cutter will remove so much material on each side of the deep cut that no key blank material is left for making an adjacent very shallow cut. Each lock company has their own MAC rule.
Before using the plug-in system you must develop the master key cuts. A good master key combination should contain one of the highest cuts in at least one space. This prevents someone from recutting another key in the system to produce a master key. The best master key cuts will have a combination of odd and even adjacent numbers. Master key cuts which use all even or all odd numbers will produce change keys with many repetitive cuts such as 44446 or 53333. These key combinations do not look secure, may allow the key to be removed in the wrong position and may be easier to pick open.
Bitting Charts
![Master Master](/uploads/1/1/7/8/117819103/916624575.jpeg)
You are now ready to develop a bitting chart and use the plug-in masterkey system. An example of Schlage master key cuts may be: 01014. The master key cut in chamber one is '0'. This leaves change key cut possibilities in the first chamber of 2468. Moving to the second chamber, the example masterkey cut '1'. This leaves change key cut possibilities of 3579. Bitting choices for the remaining chambers are chosen in the same fashion.
The resulting example key bitting array might be:
Masterkey 1: 0 1 0 1 4
Masterkey 2: 2 3 6 5 8
Masterkey 3: 6 9 4 9 0
Masterkey 4: 4 5 2 7 2
Masterkey 5: 8 7 8 3 6
Although this example bitting array shows the change key choices in a set order, any mix of the numbers could have been entered. As example, the first space numbers of 2648 could have been arranged differently such as 6284, 4682, etc..
Once you have developed a bitting array, the numbers can be 'plugged-in' to the chart. Numbers on the chart do not show actual cuts, but rather show the position of key cuts in your key bitting array. Therefore cuts for key A01 would be taken from position 2 in each space or 23658. Cuts for key A02 would be taken from position 2 except for space 5 which is position 3. Therefore A02 key cuts would be 23650, A03 cuts would be 23652 and A04 cuts would be 23656 .
If needed, HGM (horizontal master keys), VGM (vertical master keys), page master and four page master key cuts are chosen in the same way. In the example bitting array, the VGM 1-16 key is chosen from array positions 22211, or cuts of 23614. If a cylinder is set to the master key and a change key, vertical, horizontal and page master keys designed to operate the chosen change key will function without adding any additional master chips.
The complete plug-in master key system contains 16 pages with 64 codes per page, or a total of 1024 change key codes. The amount of usable combinations depends on the cut numbers chosen for your bitting array and the MAC number used by the lock manufacturer. Generally about 10 percent of the total change key and lower level master key combinations cannot be used no matter what numbers are used for your bitting list.
Page 1 of the plug-in master key system is included with this article. The remaining 15 pages can be downloaded from the Locksmith Ledger website. By choosing a new, original bitting array for each masterkeying job you do, the plug-in masterkey system charts can be used forever. Locks using single-step masterkey systems such as Kwikset can also be applied to these charts by choosing four single-step cut possibilities per chamber.
Generics can simplify how we consider and work with incidental master keys.
Figure 1. Key Bitting Array.
By using Generics, locksmiths can easily develop master keys, or develop key characteristics from key bittings.
Generics can simplify how we consider and work with incidental master keys.
The last article (October 2004 Locksmith Ledger) demonstrated how to determine the power and characteristics of a random key in the master key system by decoding the key bittings. Generic Types were used to target how the key performed within the master key system and on a page, demonstrating the power of the key.
This article will demonstrate the reverse. A Generic Type will be selected from within a master key system, and the key bitting will be determined. To do this, you will need the Key Bitting Array (KBA, Figure 1) and a worksheet specifically designed to determine key bittings from Generic Types.
Before starting, let' s review what a Generic Type is.
In Figure 2, the KEEWERX template, the mechanism that creates Generics is px. This refers to the relationship to the number of change key bittings under the master bitting. In the KBA, this is expressed as rows for change key bittings and columns for the number of key bittings.
With most systems, there are four change key bittings under the system bitting in the KBA. When 'p' in px equals 4 (the rows) and 'x' equals the 6 (the columns), the results are 41+1+1+1+1+1 or 46 or 4x4x4x4x4x4, or 4096. This is the total amount of change keys that can be progressed in a standard six-pin master key system.
Other systems have five, six or seven change bittings under the master bitting, so the 'p' in px accommodates all of these master key systems. As a system progresses, Generics are created. The term px can be used to express how the master key system progresses.
At p0, the beginning of progression is occurring in the first column. At p1, the first column is fully progressed and current progression is ready to start in the second column. At p2, the first two columns have fully progressed and current progression is starting in the third column. At p3, the first three columns have fully progressed and current progression is starting in the fourth column. At p4, the first four columns have fully progressed and current progression is starting in the fifth column. At p,5 the first five columns have fully progressed and current progression is starting in the sixth column. At p6, all six columns have been fully progressed.
Table 1 (page 36) reveals the creation of a Generic during steps of standard progression. There are only eight Generics Types: X0; X1;X2;X3; Y1; Y2; Z1; Z2.
For every three columns that progress, a new level of keys are created. The first three progressed columns create a complete hierarchy of key functions for each page of the master key system. The next three progressed columns create a hierarchy of key functions that occur within the pages of the first hierarchy.
This article is limited to Generic activity within 5- and 6-pin systems. Note that this process continues infinitely and that is there is a P7 (when dealing with 7-pin systems, etc).
Generic References for 5- and 6-pin systems are visually designed to reveal where and how the key functions. To do this, the Generic Reference is separated into two parts, a prefix and a suffix. We will examine the Generic Reference and its two components.
Consider the Generic Reference for a change key: X0X0. The first two characters represent the first Generic Type XO (the prefix), and the remaining two characters represent the second Generic Type XO (the suffix). Generic Types in the prefix position represent how the key functions throughout all pages. Generic Types in the suffix position represent how the key functions on a given page.
The numbers in both designate the power of the key. In the case of X0X0, the key operates keys on a single page, and can only operate a single change on a page (See Figure 2).
As a second example, consider the reference: X0X3. This key operates keys on a single page (p0=40), and can operate 64 (p3=43) keys on a page. Remember the numbers always reveal the power of the key (p3).
Find the Key Bittings from a Generic Type
To maintain consistency, the Key Bitting Array (KBA) and the Generic example used in the last article will be discussed: Y2X2. Refer to Figure 3 as the worksheet titled: 'Develop a Master Key (6-pin).'
To maintain consistency, the Key Bitting Array (KBA) and the Generic example used in the last article will be discussed: Y2X2. Refer to Figure 3 as the worksheet titled: 'Develop a Master Key (6-pin).'
The Key Bitting Array was filled out using the provided KBA in Figure 1.
As shown in 'Step 1,' the selected Generic (Y2X2) was split into two equal parts and entered on the 'A' and 'B' line.
In 'Step 2', any cuts in common with the TMK were identified by following the instructions: The part of the Generic that was entered on the 'A' line, 'Y2' is located to the left (row header) of the Alignment Chart. Any 6, 5, or 4 that appears on the same line in the Alignment Chart is circled. In this case a '6' and '4' was circled.
How To Master Keying Locks
The part of the Generic that was entered on the 'B' line, 'X2,' is located to the left (row header) of the Alignment Chart and any 3, 2, or 1 that appears on the same line in the Alignment Chart is also circled. In this case a '2' and a '1' was circled.
In 'Step 3' the Sequence Of Progression (SOP) from the KBA is transferred down into cells provided to the right of the step. The number in each cell is compared to numbers circled in the Alignment Chart. If a circled number in the Alignment Chart matches the number in the cell, the number in the cell is also circled.
In 'Step 4', check each cell in the 'Step 3' to see if it is circled. If it is circled enter the number from the TMK line in the KBA that appears in line with the same column. Do this for each cell. In the example the first two cells in 'Step 3' were not circled, so nothing was entered into the cells in 'Step 4'. The last four cells in 'Step 3' were circled so the numbers that appear on the TMK line of the KBA were entered into each cell of 'Step 4.'
Any change key is entered into the cells of 'Step 5.' This is usually a change key that is being used for a specific master key project in which a master key is needed.
![Master keying Master keying](/uploads/1/1/7/8/117819103/788137042.jpg)
The final step, 'Step 6,' integrates both the selected change key ('Step 5') and the cells that were entered in 'Step 4.' For each cell to the right of 'Step 6,' enter the same number, in the same position, from 'Step 4'. If the cell is blank, enter instead, the number from the cell in the same position from 'Step 5'.
When completed, the key bitting for the master key, Y2X2, appears on 'Step 6.'
A blank worksheet (Figure 4) is provided so that you can use this procedure to determine master keys for your own master key systems. Although the worksheet seems to work like a magician's number trick, it simply relies on the tried-and-true premises already established in Standard Progression Format (SPF). Each step in the worksheet is designed to 'guide' the locksmith through a process that enforces SPF rules.
A crucial step in the worksheet is guiding the locksmith through the implementation of the Alignment Chart. The chart is deceivingly simple, even though much research has gone into its creation. The Alignment Chart is a table that notes when and where TMK bittings will appear in a targeted key. It charts the evolution of master keys as keys sequentially progress. The Alignment Chart in Figure 3 is designed for both 5- and 6-pin systems.
Developing a Key Bitting Array when it doesn't exist
Essential to good master keying procedure is the establishment of a static Key Bitting Array.
Essential to good master keying procedure is the establishment of a static Key Bitting Array.
Locksmiths tell me many of their existing master key systems do not come with a KBA, rather they exist in the form of pages of records. Lock manufacturers often provide these pages to locksmiths, not as a complete 'book' but as the part of the 'book' that the locksmith currently needs. For these locksmiths, there is a process to determine the original Key Bitting Array.
When information is not readily available to complete the KBA, a decision has to be made. If support regarding the existing system is ongoing, you will need to discuss the completion of the KBA with the source of the existing system.
If no updates are anticipated, the KBA can be carefully filled-in by honoring the rules of Standard Progression Format.
Here are the rules to follow:
Regarding the sequence of progression, each number represents the order in which the columns progress; therefore, numbers have to be sequential and cannot be repeated in the SOP.
Regarding the sequence of progression, each number represents the order in which the columns progress; therefore, numbers have to be sequential and cannot be repeated in the SOP.
When filling in missing change progressions, remember that TMK bittings (in the same column position) must not appear in the change progression cells. This would cause unwanted interchanges of change keys.
Master Keying Guide Questions
Each column of change progression cells must use unique numbers that are part of a working subset for the column. For example, in any given column a working subset might be {1,3,5,7,9}. If the TMK bitting is 5, then the remaining available numbers are the subset {1,3,5,9}. In a column of change progression cells, these four numbers would be entered in the cells in any order.
Once the KBA has been established, all worksheets described in this article can be implemented.
Table 1. Creation of a Generic
Master Keying Guide App
Developing Columns | Generic Types Produced | Hierarchy |
---|---|---|
PO | XO | Changes on a Page |
P1 | X1;Y1;Z1 | Changes on a Page |
P2 | X2;Y2;Z2 | Changes on a Page |
P3 | X3 | Changes on a Page |
P4 | X0 | Pages in a System |
P5 | X1, Y1, Z1 | Pages in a System |
P6 | X2, Y2, Z2 | Pages in a System |