CPL Troubleshooting & Repair of Locks 2

Question 1

A mortise lock cylinder spins freely when the key is turned but does not retract the bolt. What is the most likely cause?

Accepted Answer

Broken cam or tailpiece

Answer

A freely spinning cylinder with no bolt movement indicates the cam or tailpiece connecting the cylinder to the bolt mechanism is broken or detached.

Question 2

Which lubricant is generally recommended for pin tumbler lock cylinders to avoid attracting dirt and debris?

Accepted Answer

Graphite powder

Answer

Graphite powder is the preferred dry lubricant for pin tumbler cylinders because it does not attract dirt or gum up the internal components.

Question 3

A wafer tumbler lock is difficult to turn even after the correct key is inserted. Which condition is the most probable cause?

Accepted Answer

Worn or deformed wafers binding in the housing

Answer

Worn or bent wafers that drag against the housing create binding, making the lock hard to turn even with the correct key.

Question 4

When disassembling a pin tumbler cylinder for repair, a follower tool is used primarily to:

Accepted Answer

Keep the driver pins and springs from falling out

Answer

A follower maintains pressure on the driver pins and springs so they stay seated in the shell when the plug is removed.

Question 5

A deadbolt throws only halfway before stopping. After ruling out hinge and door alignment issues, what internal component should be inspected next?

Accepted Answer

A broken or weak bolt spring

Answer

A weak or broken bolt spring can prevent the deadbolt from completing its full throw, causing it to stop partway.

(CPL) Certified Professional Locksmith Practice Test