CPL Pin Tumbler & Cylinder Mechanisms 3 — Questions and Answers
Question 1: What is 'key control' as it relates to pin tumbler cylinders?
- Limiting who can duplicate keys by using patented or restricted keyways (Correct answer)
- Controlling the depth of key cuts during rekeying
- Measuring key bow dimensions for proper grip
- Setting the number of active pin chambers
Correct answer: Limiting who can duplicate keys by using patented or restricted keyways
Key control refers to restricting unauthorized key duplication, typically through patented keyways, restricted blanks, or high-security cylinders.
Question 2: When rekeying a pin tumbler lock, which set of pins is typically replaced?
- Driver pins only
- Springs only
- Key pins (bottom pins) to match the new key bitting (Correct answer)
- The entire plug assembly
Correct answer: Key pins (bottom pins) to match the new key bitting
Rekeying involves replacing the key pins with new ones of different heights so the lock operates only with the new key.
Question 3: A 'false set' during picking occurs when:
- The plug rotates slightly because some pins are set but at least one driver pin still blocks (Correct answer)
- The key is inserted upside down
- All pins are set but the cam does not retract
- The tension wrench breaks inside the cylinder
Correct answer: The plug rotates slightly because some pins are set but at least one driver pin still blocks
A false set happens when enough pins are set to allow slight plug rotation, but at least one driver pin is still crossing the shear line, preventing full rotation.
Question 4: What is the function of the plug follower in cylinder servicing?
- To hold the driver pins in place while the plug is removed, preventing them from falling (Correct answer)
- To re-spring the key pins after rekeying
- To measure plug diameter for replacement
- To align the cam with the tail piece
Correct answer: To hold the driver pins in place while the plug is removed, preventing them from falling
The plug follower is inserted behind the plug as it is removed, maintaining pressure on driver pins and springs so they do not fall out of the shell.
Question 5: Which measurement system is most commonly used in the US to specify pin tumbler key cut depths?
- Metric millimeters only
- Fractional inches (1/32" increments)
- Numeric depth codes assigned by the manufacturer (Correct answer)
- Alphanumeric bitting codes (A–Z)
Correct answer: Numeric depth codes assigned by the manufacturer
US lock manufacturers assign numeric depth codes (e.g., 1–9) to represent specific cut depths, making it easier to reference bitting without precise measurements.
Question 6: What does 'MACS' (Maximum Adjacent Cut Specification) govern in key cutting?
- The maximum number of master pins allowed per cylinder
- The largest allowable depth difference between any two adjacent key cuts (Correct answer)
- The minimum key blank length required
- The maximum number of key duplications allowed
Correct answer: The largest allowable depth difference between any two adjacent key cuts
MACS defines the greatest permitted depth difference between neighboring cuts on a key; exceeding MACS can prevent the key from operating the lock or damage the cylinder.
Question 7: In a high-security pin tumbler cylinder, sidebar mechanisms provide additional security by:
- Increasing spring tension on driver pins
- Requiring an additional set of elements (sidebar pins or sliders) to align before the plug rotates (Correct answer)
- Doubling the number of key cuts required
- Using magnetic pins instead of metal pins
Correct answer: Requiring an additional set of elements (sidebar pins or sliders) to align before the plug rotates
Sidebar cylinders add a secondary locking element (the sidebar) that must retract—by aligning sidebar pins or sliders—before the plug can rotate, defeating standard picking.
CPL Pin Tumbler & Cylinder Mechanisms 3
What is 'key control' as it relates to pin tumbler cylinders?