A lock master pin, in the context of pin tumbler locks, is an additional pin component inserted into one or more chambers of the lock cylinder to enable multiple keys to open the same lock. It creates an extra shear point within the cylinder.
How Master Pins Work
A standard pin tumbler lock works by having a series of pins that need to be aligned at a specific shear line in order for the cylinder to rotate and the lock to open. A correctly cut key pushes each pin stack (driver pin and key pin) into the correct position.
A master pin adds another layer of complexity. Here's a breakdown:
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Standard Pin Tumbler Lock: Each chamber contains a key pin (touches the key) and a driver pin (above the key pin). When the correct key is inserted, the gap between the key pin and driver pin aligns at the shear line, allowing the cylinder to turn.
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Master Keyed Lock: In a master keyed lock, one or more chambers will have a master pin between the key pin and driver pin. This master pin allows for two possible shear points in that chamber. The master key and the change key both create a shear point, albeit at different positions. Therefore, both keys will operate the lock.
Function of a Master Pin
The primary function of a master pin is to:
- Create an alternative shear point: This allows a key that's different from the original to also open the lock.
- Enable master keying systems: These systems allow a hierarchy of keys, where one "master" key can open all locks in a system, while individual "change" keys only open specific locks.
- Increase Lock Complexity: Adding master pins adds a greater number of possible key combinations and overall lock complexity.
Example
Imagine a hotel. Each guest room has a unique key (change key). A master key allows staff to access any room in the hotel. In this case, the locks on the hotel rooms would contain master pins. These master pins allow the guest's key AND the master key to create a shear point, allowing the cylinder to turn.
