History and Design of Lever Tumbler Locks
– Invented in 1778 by Robert Barron of England
– Double acting lever tumbler locks are still used today on doors in Europe, Africa, South America, and other parts of the world
– Five-lever locks are designed to be mortised into a door
– Lever locks generally use a bitted key
– Some locks used on safes and door locks in Southern and Eastern Europe use a double-bitted key
– Lever locks are made up of levers usually made out of non-ferrous metals
– Each lever needs to be lifted to a specific height by the key for the locking bolt to move
– Lever locks have pockets or gates through which the bolt moves during unlocking
– Different variants of lever locks have different designs and combinations
– Lever locks can be categorized as lever locks or detainer locks based on the location of the gates
Types of Lever Tumbler Locks
– Three-lever locks
– Commonly used for low-security applications such as internal doors
– Tolerances are lower, resulting in fewer key combinations
– Not recommended for high-security purposes
– Provide basic security for applications like mailboxes, luggage, and lockers
– Limited master-key combinations compared to pin tumbler locks
– Five-lever locks
– Often required for home insurance and recommended by the police for home security
– Various grades available, with the current British Standard (BS3621:2007) being the most common for insurance purposes
– BS3621:2007 requires a bolt throw of 20mm for increased security
– Most BS3621 locks have anti-pick devices, hardened bolts, and anti-drill plates
– Historic churches often have old wooden locks alongside modern 5-lever mortice locks to meet insurance requirements
Vulnerabilities of Lever Tumbler Locks
– Lever tumbler locks can be picked using curtain picks to lift each lever to the correct height
– Higher security lever locks have notches that catch the locking bolt to prevent picking
– The Chubb detector lock was designed to detect and prevent picking attempts
– Lever locks can be drilled, but a template or stencil is needed to mark the drilling point
– Lever locks have vulnerabilities that can be exploited if not properly secured
Components and Functioning of Lever Tumbler Locks
– Case or housing
– Keyway
– Key
– Levers
– Springs
– Key lifts levers to correct height
– Levers align with shear line
– Allows rotation of the lock cylinder
– Incorrect key heights prevent rotation
– Number of levers varies in different locks
Advantages and Applications of Lever Tumbler Locks
– Advantages:
– Difficult to pick due to multiple levers
– Provides high level of security
– Can be master-keyed for convenience
– Durable and long-lasting
– Relatively simple design
– Applications:
– Residential doors
– Commercial buildings
– Safes and vaults
– Cabinets and drawers
– PadlocksSources: https://en.wikipedia.org/wiki/Lever_tumbler_lock
