CML Lock Mechanisms & Hardware 5 — Questions and Answers
Question 1: What does 'key bitting array' (KBA) refer to in a master key system?
- The total number of keys that can be cut for a given lock
- The complete set of all possible bitting combinations available in a key system (Correct answer)
- The physical arrangement of cuts on a specific key
- The manufacturer's code used to identify a key blank
Correct answer: The complete set of all possible bitting combinations available in a key system
The key bitting array is the full matrix of all theoretically possible key bittings for a given lock's specifications (depths, cuts, and spaces), from which a master key system designer selects combinations.
Question 2: What is a 'mogul' cylinder and where is it typically used?
- An oversized cylinder (1-1/2" diameter or larger) used in high-traffic institutional or government applications (Correct answer)
- A proprietary cylinder design used exclusively by BEST Access Systems
- A small-format interchangeable core used in office furniture
- A cylinder with an extended cam for use in thick doors
Correct answer: An oversized cylinder (1-1/2" diameter or larger) used in high-traffic institutional or government applications
Mogul cylinders have a larger-than-standard diameter (typically 1-1/2 inches or greater) and are used in high-security government, institutional, and transit applications requiring increased key control and durability.
Question 3: In a disc detainer lock, what replaces the pin tumblers as the blocking mechanism?
- Lever tumblers with individual springs
- Rotating discs with slots that must align to allow the bolt carrier to rotate (Correct answer)
- Spring-loaded ball bearings at multiple positions
- A single precision-machined cam with multiple locking points
Correct answer: Rotating discs with slots that must align to allow the bolt carrier to rotate
Disc detainer locks use a stack of rotating discs, each with a slot cut at a specific angle; the correct key rotates each disc to the right position so all slots align, allowing the core to rotate.
Question 4: What is the 'total position' (TP) in master key system design?
- The total number of key positions (cuts) on a key blade
- The total count of all pin stacks in a cylinder
- The sum of all depth values across all cut positions on a key (Correct answer)
- The number of change keys that can operate under a single master key
Correct answer: The sum of all depth values across all cut positions on a key
Total position (TP) is calculated by adding the depth values of all cuts on a key, and keys in a master key system must maintain minimum and maximum TP differences to ensure they cannot accidentally cross-operate.
Question 5: A locksmith notices that a commercial door's latch is not catching the strike plate and the door rattles. What hardware component adjustment is FIRST recommended?
- Replace the entire lockset with a higher-grade unit
- Adjust the strike plate position or install a strike plate with a larger opening (Correct answer)
- Replace the latch bolt spring inside the lockset
- Plane the door edge to move the latch centerline
Correct answer: Adjust the strike plate position or install a strike plate with a larger opening
Strike plate misalignment is the most common cause of a latch not catching; adjusting the strike plate position or installing a strike with an oversized opening is the standard first-line correction before modifying the door or lockset.
Question 6: Which ANSI door hardware function number designates a classroom lock (key locks/unlocks from outside, always free from inside)?
- Function F04
- Function F05
- Function F84
- Function F13 (Correct answer)
Correct answer: Function F13
ANSI Function F13 (classroom function) is keyed from the outside only, with the inside lever always free to exit, making it the standard function for school and classroom applications.
Question 7: What is the purpose of a 'cutout' or 'relief cut' on a key bow or shoulder stop?
- To reduce the weight of the key blank for easier carrying
- To serve as a depth reference or positive stop that positions the key blade consistently in the cylinder (Correct answer)
- To indicate the key blank manufacturer's series designation
- To allow the key to be folded for compact storage
Correct answer: To serve as a depth reference or positive stop that positions the key blade consistently in the cylinder
The shoulder stop (or tip stop on tip-operated systems) is a precise reference point that ensures the key blade seats at the same depth each insertion, guaranteeing consistent alignment of each cut with its corresponding pin stack.
CML Lock Mechanisms & Hardware 5
What does 'key bitting array' (KBA) refer to in a master key system?