Every locksmith worth his salary knows how to add master pins to a pin tumbler lock to allow both a change key and master key to operate. A lesser used, but important procedure, is the masterkeying of disc tumbler locks. Disc tumbler locks require not only the proper type of plug design to accept...
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A few words of caution. Since all of the possible key cuts are being used, every masterkey system developed in this manner will be using the same 243 key codes. Codes can be used in different orders, but it will always be the same 243 codes. For security or esthetic reasons, approximately 10 percent of the codes should not be used due to repetitive cut numbers such as four or five of the same cuts in a row.
Another system for generating change keys in a master key system is called rotating constant. Chart 1 illustrates a rotating constant system where cuts in two spaces are identical to the master key while three spaces are rotated.
Ten different rotational combinations are available in a five space system when using master discs in three spaces and keeping the remaining spaces identical to the master key cuts. Spaces identical to the master key are 12, 13, 14, 15, 23, 24, 25, 34, 35, 45. Each different rotation combination is shown in the 10 groups of Chart 1.
Your choice of master key cuts dictates what the change key cuts will be. This provides a different variety of change key cuts for each small masterkey system. Note that some change key cuts such as #16 (22222) and #55 (11111) are usable, but not recommended because of their repetition of cuts.
There is one last hurdle to overcome when pinning disc tumbler locks. In order to make disc tumbler locks as compact as possible, most lock companies stagger the spring chambers. Photo 5 shows a disc tumbler lock made by Fort Lock. Notice that the first spring chamber is to the right, the second spring chamber to the left, etc..
Disc tumblers contain a spring tab. If a lock plug uses staggered spring chambers then the tumbler must be rotated 180 degrees from space to space during pinning in order to insert the spring tab into the spring chamber. This means that when a tumbler with stepped depths of 2/left & 1/right is rotated 180 degrees, the cuts suddenly change to 1/left & 2/right. Photo 1 shows the effect of moving the spring perch from right to left.
Pinning kits will contain duplicate pairs of stepped discs, one of which will have the tab to the left, while the other will have the tab to the right. The CCL keying kit contains six master tumbler types (0/1 & 1/0)(0/2 & 2/0)(1/2 & 2/1). In addition there are three non-mastered tumbler numbers 0,1 & 2. These nine different tumblers allow for any combination of master and change key cuts using 0,1 & 2 depths regardless of the spring orientation.
For more information on CCL products, contact your local distributor or: CCL, telephone 800-733-8588.
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