Locksmith Lock Mechanisms 2 — Questions and Answers
Question 1: What is the primary function of the shear line in a pin tumbler lock?
- It lubricates the plug rotation
- It separates driver pins from key pins when the correct key is inserted (Correct answer)
- It holds the springs under tension
- It connects the plug to the cam
Correct answer: It separates driver pins from key pins when the correct key is inserted
The shear line is the gap between the plug and shell where driver pins separate from key pins, allowing the plug to rotate when the correct key lifts all pins to the proper height.
Question 2: A wafer lock differs from a pin tumbler lock primarily because it uses:
- Rotating discs instead of pins
- Flat spring-loaded wafers instead of stacked pin pairs (Correct answer)
- Magnetic fields to hold the plug
- A sidebar mechanism for additional security
Correct answer: Flat spring-loaded wafers instead of stacked pin pairs
Wafer locks use single flat wafers that spring into slots in the shell, unlike pin tumbler locks which use pairs of driver and key pins.
Question 3: In a disc detainer lock, what holds the plug from rotating when no key is inserted?
- A row of spring-loaded pins
- Rotating discs whose slots are misaligned with the sidebar (Correct answer)
- A deadbolt engaged by a cam
- Magnetic repulsion between rotor and stator
Correct answer: Rotating discs whose slots are misaligned with the sidebar
Disc detainer locks use rotating disc tumblers with slots; when no key is present, the slots are misaligned and prevent the sidebar from retracting, blocking plug rotation.
Question 4: Which component in a pin tumbler lock provides upward pressure on the driver pins?
- The plug warding
- The bible springs (Correct answer)
- The cam follower
- The retainer clip
Correct answer: The bible springs
Bible springs (pin springs) sit above each driver pin in the shell and push the driver pins downward into the plug, keeping the lock secure without a key.
Question 5: What is 'master keying' achieved by in a standard pin tumbler lock?
- Installing a second plug with different keyway warding
- Adding additional pin stacks with master wafers to create extra shear lines (Correct answer)
- Replacing driver pins with mushroom pins throughout
- Drilling a bypass hole in the shell
Correct answer: Adding additional pin stacks with master wafers to create extra shear lines
Master keying adds master wafers (small spacer pins) between the key pin and driver pin, creating extra shear line positions that multiple keys can use.
Question 6: A mortise lock cylinder differs from a key-in-knob cylinder primarily in that it:
- Uses wafers instead of pin tumblers
- Has a threaded exterior and cam that engages a mortise case mechanism (Correct answer)
- Cannot be rekeyed without replacing the entire unit
- Is always double-sided for two-key operation
Correct answer: Has a threaded exterior and cam that engages a mortise case mechanism
Mortise cylinders have a threaded body that screws into a mortise case and include a cam on the back that actuates the lock case components when rotated.
Question 7: What is the purpose of warding in a lock keyway?
- To provide lubrication channels for the key blade
- To restrict which key profiles can enter the keyway (Correct answer)
- To strengthen the plug against drilling attacks
- To align the key with the shear line
Correct answer: To restrict which key profiles can enter the keyway
Warding refers to the projections and grooves in the keyway that prevent keys with incorrect profiles from being fully inserted, providing a basic level of key control.
Locksmith Lock Mechanisms 2
What is the primary function of the shear line in a pin tumbler lock?