The complete Bramah lock can be disassembled into the following parts:
- A brass back plate and top surface plate (often marked Bramah – London or Bramah – 124 Piccadilly, London etc)
- A turned brass central cylinder containing a number of intricately cut, folded steel wafers, a cylinder back plate with a central pin, a central spring, and a central brass disc that fits over the pin. Note: Most Bramah box locks have an inset stud on the rear of the cylinder back plate, however, self-locking versions, as well as some standard versions used a cylinder arm instead – see ‘Operating a Bramah Lock’ below for explanation.
- Two halved steel incised plates that engage with the central cylinder and wafers.
- A turned brass lock mount and front aperture unit.
- A brass or steel lock slider with or without an attached guide plate. Note: Self-locking Bramah locks didn’t require a guide plate.
- A brass lock slider support bracket that attaches to the back plate. Note: Self locking Bramah locks weren’t often manufactured to require this bracket.
- A mounted steel spring that attaches to the back plate. Note: These were only required for self-locking Bramah locks.
- A brass or steel top locking plate with lugs to engage with the lock slider.
- A key with incised bits at varying different depths at the end of the barrel.
Operating a Bramah Lock
- The key enters the front lock aperture, making contact with the central lock pin; the incised bits at the end of key barrel engage with the spring-loaded steel wafers. These wafers are incised at exact points to correspond with the incised bit depths of the key. When the key is properly pushed in, the wafer incisions all align together, allowing the halved plates surrounding the central cylinder to be unobstructed. The central cylinder is now rotatable.
- The key can now be turned anti-clockwise, rotating the central cylinder that is either, inset with a rear stud that engages with the guide plate attached to the lock slider, or, affixed with an arm that engages with an incised ridge on the lock slider.
- The lock slider is deployed at about the 90-180 degree mark and moves from right to left in most cases. Note: For self-locking Bramah locks, the key is turned clockwise by about -45 to -90 degrees; this action rotates the central cylinder and cylinder arm that then engages with an incised ridge on the lock slider, pushing it back against the mounted steel spring, thus disengaging the lock mechanism. The lock slider will automatically spring back into its locked position as soon as the pressure from the key turning action is released.
- With the lock slider now in the locked position, the key can complete its anti-clockwise turn back to the 0 degree mark, where it can naturally ‘pop’ out from the front lock aperture using the initial spring-loaded mechanism behind the wafers.
- Unlocking the Bramah lock is a simple case of reversing the locking procedure; the key is re-inserted, pressed in, and now turned clockwise by 360 degrees back to the 0 degree point where again it will ‘pop’ out from the front lock aperture.