Unlike other commercial lock cylinders, figure-eight (small format) interchangeable cores require special removal techniques when keys are not available. Interchangeable cores are normally removed by inserting the control key then turning the key clockwise about 15 degrees. When the rotation...
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Remember that picking these types of cores is always challenging and is not guaranteed. Picking is always the preferred method if time allows or if the core cannot be sacrificed. When time is an issue, drilling consistently offers a predictable time of completion.
Drilling to Preserve Pin stacks for Decoding
I prefer drilling to picking as it is a sure thing and the cost of core replacement is less than the cost of time to pick the core. Figure 6 features a “marking” tool I created by pinning a broken key blank and plug together. I simply insert the marking tool and score the core or cylinder. This gives me an exact drilling location.
Successful core drilling is like safe work, knowing where to drill and drilling clean holes, is essential. It is better to take your time and use a sharp drill versus brute force and over-sized holes.
In Figure 7 a “clean”, 1/4” hole is precisely drilled, removing all parts of the mortise cylinders face that normally secures the core. Once the face plate is penetrated it is easily pried out with a small screwdriver. Figure 8 is a close up of the finished hole. Figure 9 is a sectional view of all the pins in a typical seven-pin core.
It was necessary to “sacrifice” this mortise cylinder to keep the core intact. With the core in-hand, it can now be carefully disassembled and the control key decoded.
To decode the control key, the driver pins (in the sectional view those colored red) must be extracted in proper order then identified by determining pin lengths. The pin length can be compared to the manufacturer’s numbering designation.
The formula to determine the cut of a control key in a specific chamber is to take the value of the pin number designation and subtract it from 13. For instance, if a driver pin has been determined to be a #4 driver segment, subtract 4 from 13 to get 8. The cut of the control key in that chamber position will be 8.
This can be done by hand by carefully inserting a pin extractor at the bottom of a core and then carefully tapping it with a hammer holding pressure on that chamber with your finger. When you feel the retainer cap give, carefully elevate the pin stack and spring with the extractor.
The spring is the first component to be elevated out of the chamber. Directly following it is the driver pin to be decoded.
Although this technique requires a minimum of tools, it is a learned technique, requires practice, and is not as quick as specialized designed tools for the task. Figure 10 is an interchangeable decoding kit that streamlines the process.
To decode the heights of pins, use a dial caliper like the one shown in Figure 11.
With a key gauge, colored driver segments, and super glue, I created a visual gauge that allows me to quickly identify pins and relate them to control cuts without doing the math. I started by gluing a #4 segment across from the 9 hatch-mark and then worked up. When I visually identify the pin height I just glance up at the cut number. Figure 12 is an image of the altered key gauge.
Drilling When Decoding is not Necessary
Most of my work involves failed cores that no longer work with operating or control keys. This doesn’t mean that interchangeable cores prematurely wear out, but there are locations in which all commercial cores or cylinders will quickly wear out. This is a routine occurrence with me as many of the locks I service are opened hundreds of times each day.
The quick solution is to drill the core out and swap it.
There are two methods, my personal favorite, and that recommended by the manufacturer.
The first step regarding my personal favorite is to use the marking tool to score the drill location. This is shown in Figure 13.
Once scored, I insert a blank key to raise the pins and then use a 3/32” pilot hole to drill thru all chambers (see Figure 14).
Changing drill bits to a sharp #7, I increase the diameter of the hole (see Figure 15). The sharp hole creates a new shear line then the key blank is rotated to the removal position (see Figure 16).
The next method is the traditional means recommended by the manufacturer.
Lock manufacturers are depended upon to control the issuance of key stock.
A1 Security Manufacturing Corporation manufactures a variety of tools for the institutional/commercial locksmith. These include key origination machines, installation equipment, lock picks, and...