Interchangeable core

An interchangeable core or IC is a compact keying mechanism in a specific "small format" figure-eight shape. Unlike a standard key cylinder, which is accessible for combinating only via locking device disassembly, an interchangeable mechanism relies upon a specialized "control" key for insertion and extraction of the essential (or "core") combinating components.

Interchangeable cores can be extracted from one lock type (bored cylindrical lock, mortise lock, padlock and so forth) and then installed into another without requiring the removal or disassembly of any single component. These units are readily adapted for master keying systems and can be set up with spare cores and keys for quick replacement when security is compromised, such as when a key is lost or stolen or when a personnel change takes place. Extracted cores can then be recombinated without urgency and placed back into maintenance storage for future use.

Although operationally similar to removable cores, which come in varying "large format" snowman shapes, interchangeable cores neither dictate nor exclude the use of a particular hardware manufacturer. In other words, whereas a typical large format key system of Brand X must be expanded with Brand X cores and must use Brand X cylindrical locks and cylinder housings, a typical small format key system of Brand A can be expanded with cores from Brands A, B, C, D, E and so on, and can also be used with locks and housings from Brands A, B, C, D, E and so on.

Interchangeable cores require a notch at the tip of each key to properly align the peaks and valleys of each blade with the combinating pins in the chambers of the mechanism; as a consequence, these keys are always configured and cut from blade tip to bow. Conversely, conventional cylinders and removable cores use a shoulder near the bow of each key to properly align all peaks and valleys; as a consequence, these keys are always configured and cut from bow to blade tip. As a further consequence of this fundamental difference, neither of these two key types can ever be cross- or master-keyed with the other.

As a benefit to keying from blade tip to bow, a six- or seven-pin interchangeable core key blank can be machined to precisely fit a smaller five-pin system configuration. Although the blade of such keys may be a pin or two longer than need be, this extra length never enters the locking mechanism; therefore, five-, six- and seven-pin interchangeable core systems can be easily integrated to work with one another or to provide different levels of access control within the same system. Conventional cylinder and removable core systems are significantly more limited in this regard since the extra length of their keys must pass through to the inside of the locking mechanism, which is often just not physically possible.

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