CML Lock Mechanisms & Hardware 3 — Questions and Answers
Question 1: What is the function of the control lug on a removable-core (BEST-type) cylinder?
- It locks the core to the housing when a regular key is used
- It retracts when the control key is inserted, allowing the core to be removed from the housing (Correct answer)
- It prevents the plug from rotating more than 180 degrees
- It engages the cam to operate the locking bolt
Correct answer: It retracts when the control key is inserted, allowing the core to be removed from the housing
The control lug engages the housing to retain the core; inserting the control key retracts this lug, allowing the core to be pulled out and replaced without tools.
Question 2: In a wafer tumbler lock, what prevents the plug from rotating when the wrong key is inserted?
- Driver pins that bridge the shear line
- Wafers that extend into the shell's slots when not lifted to the correct height (Correct answer)
- A sidebar that engages the shell groove
- Spring-loaded ball bearings that lock into the plug
Correct answer: Wafers that extend into the shell's slots when not lifted to the correct height
In wafer locks, each spring-loaded wafer protrudes into a groove in the shell; the correct key lifts all wafers flush with the plug's outer diameter, clearing the shell grooves and allowing rotation.
Question 3: A Grade 1 commercial lockset, per ANSI/BHMA standards, is rated for a minimum of how many cycles?
- 100,000 cycles
- 250,000 cycles
- 500,000 cycles (Correct answer)
- 1,000,000 cycles
Correct answer: 500,000 cycles
ANSI/BHMA Grade 1 is the highest commercial grade and requires the lockset to withstand a minimum of 500,000 operational cycles.
Question 4: What is the main mechanical difference between a mortise lock and a cylindrical (bored) lockset?
- A mortise lock uses a rim cylinder while a cylindrical lockset uses a mortise cylinder
- A mortise lock is a complete locking mechanism housed in a rectangular case mortised into the door edge, while a cylindrical lockset's components mount through bored holes (Correct answer)
- A mortise lock always includes a deadbolt while a cylindrical lockset never does
- A mortise lock is keyed from one side only while a cylindrical lockset is keyed from both sides
Correct answer: A mortise lock is a complete locking mechanism housed in a rectangular case mortised into the door edge, while a cylindrical lockset's components mount through bored holes
A mortise lock body is a self-contained unit inserted into a pocket (mortise) cut into the door edge, whereas a cylindrical lockset is installed through drilled holes in the door face and edge.
Question 5: What does the term 'key cut depth' refer to in key specifications?
- The total length of the key blade from tip to bow
- The vertical distance from the key's shoulder to the lowest point of a given cut (Correct answer)
- The horizontal spacing between adjacent cuts on the key blade
- The angle at which the key blade is inserted into the keyway
Correct answer: The vertical distance from the key's shoulder to the lowest point of a given cut
Key cut depth is the vertical measurement from the key's reference line (shoulder or tip) to the bottom of each individual cut, determining how far each pin is lifted.
Question 6: Which type of lock cylinder is most commonly found in a standard residential knob or lever lockset?
- Mortise cylinder
- Rim cylinder
- Interchangeable core cylinder
- Cylindrical (key-in-knob) cylinder (Correct answer)
Correct answer: Cylindrical (key-in-knob) cylinder
Cylindrical (key-in-knob or key-in-lever) cylinders are specifically designed to fit inside the rotating knob or lever housing of bored locksets and are the most common residential cylinder type.
Question 7: In a pin tumbler lock, what is the 'bible'?
- The manufacturer's key bitting specification document
- The portion of the lock housing containing the pin chambers above the plug (Correct answer)
- The metal plate covering the back of the lock case
- The spring-loaded arm that prevents unauthorized key duplication
Correct answer: The portion of the lock housing containing the pin chambers above the plug
The 'bible' is the colloquial term for the upper portion of the lock shell or housing that contains the driver pin chambers and springs above the plug.
CML Lock Mechanisms & Hardware 3
What is the function of the control lug on a removable-core (BEST-type) cylinder?