Overview
This lecture explains how a pin tumbler lock operates and how master key systems allow multiple keys to open the same lock.
Parts of a Pin Tumbler Lock
- The Case is the outer shell of the lock.
- The Plug is the inner part that turns when the lock opens.
- The Keyway is the slot where the key is inserted.
- Vertical shafts inside the lock contain Springs, Driver Pins, and Key Pins.
How the Pin Tumbler Mechanism Works
- Springs push the Driver Pins and Key Pins down onto a ledge inside the lock.
- Each key has unique ridges that raise Key Pins to specific heights.
- The Shear line is where the Plug meets the Case, and all pins must align here for the Plug to turn.
- Inserting the wrong key misaligns the pins, preventing the Plug from rotating.
- The correct key aligns all pins at the Shear line, allowing the Plug to turn and unlock.
Master Key Systems
- In buildings with many locks, a Master key can open all doors by using extra pins called Master Pins in some shafts.
- The presence of Master Pins allows either a regular key or the Master key to align pins at the Shear line.
- Some systems have Master Pins in multiple shafts to accommodate multiple keys.
Key Terms & Definitions
- Case — the outer shell of the lock.
- Plug — the inner part that turns to open the lock.
- Keyway — the slot where the key is inserted.
- Shear line — the interface where the Plug meets the Case; pins must align here to turn the lock.
- Key Pin — the pin that touches the key and is raised to a specific height.
- Driver Pin — the pin above the Key Pin, pushed down by the spring.
- Spring — presses the pins down into the Plug.
- Master Pin — an extra pin that allows both regular keys and a Master key to work in the same lock.
Action Items / Next Steps
- Review the operation of pin tumbler locks and master key systems.
- Optional: Watch the recommended video on door handles for additional understanding.