In a 5-pin key system, the possible four-part rotation sequences are 1234, 1235, 1245, 1345, 2345. The basic rule for rotating constant is that every change key cut in the system will contain at least one cut from the top master key. A top master key is chosen and a key bitting array of available change key cuts are developed for each space on the keys. Rotating constant key systems begin development just like hold & vary. Devine left off, and locksmiths of today have easier, more accurate ways to generate master key programs.ĭuring the mid 1980s I became employed by Abloy Security Locks and was sent to Finland to learn about a different master key system called rotating constant. Master keys which operate larger amounts of pages are available for 6-pin and 7- pin systems.Ĭomputerized master key programs took up where Mr. There is a master key which operates each page, a master key which operates each four pages plus vertical and horizontal master keys for groups of 16 change keys on each page. A 5-pin system contains 16 pages, a 6-pin system contains 64 pages and a 7-pin system contains 128 pages. Depending on the allowable maximum adjacent cut (MAC), usable change keys may be approximately 10 percent less than theoretical change key amounts.Ī quadrant system automatically provides pages of 64 codes per page. A five pin system automatically develops 1024 theoretical change keys, a 6-pin system develops 4096 theoretical change keys and a 7-pin system develops 16384 theoretical change keys. Hold & Vary quadrant systems provide a set amount of change keys and master keys. Fortunately the same Devine formulas still apply, the only result is that more or less change keys are available as dictated by the amount of cuts in the key bitting array. While commercial locks such Schlage, Sargent and Yale fit easily into the quadrant system formula, companies such as Kwikset, Dominion and others either used a single step system or had less than 10 depth increments with which to produce a true quadrant key system. Devine, a locksmith could set up an array of numbers and plug the real numbers in place of the Devine symbols and build a master key system with new key cuts for every job. Armed with the symbol charts developed by Mr. Devine developed a single typewriter symbol for each possible individual top master key cut and each cut in the key bitting array and showed by symbols how each top master key, lower level masterkey and all change keys could be cut. When rules of hold & vary are followed, the lock cylinders are not worn or mutilated, correct pin lengths are used and keys are cut to manufacturer depth/space tolerances, hold & vary is a foolproof system to implement. The basic rule for a hold & vary key system is that all change key cuts are taken from the key bitting array list and all lower level master keys are developed by using a combination of change key cuts and top master key cuts. A setup chart for hold & vary systems contains the top master key cuts and a key bitting array listing of the change key cut choices which can be used in each space on the change keys. This provided one master key cut and four remaining cuts which could be used for the change keys. By coincidence, popular key systems such as Sargent, Yale and Schlage used a 10 depth increment system and a two-step progression. Hollis Devine is often credited with developing a master key system in the 1960s which is known under various names such as The Quadrant System or Hold & Vary. When a customer required floor master keys or if all change keys had to operate a vestibule door, these key systems were not very helpful. The problem with these one-size-fits-all master key systems was that it was just a list of change keys. At least then there were more code systems to choose from. Several enterprising locksmiths later published books of master key systems. If a second master key system was required, we reversed the cuts tip to bow and used the same Reed master key system one more time. As the same cuts were used over and over again, notes written in the margins showed what keyways had already been used. My early recollections of developing master key systems included the use of a master key system printed in the beginning pages of the leather-bound Reed Code Book.
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