Why do keys and locks wear?
Each time a key is inserted and removed from a lock, it rubs against pins or wafers. The friction caused by this action actually wears away metal from the key and the pins inside of the lock. After thousands of times, the key thins and becomes increasingly difficult to copy. Key wear is often evident on an old car key or a house key. Locks also wear. The action of inserting the key into the lock wears the milling of the lock, widening the space the key slides into. Locks used with the most frequency wear the most, such as restrooms in office buildings, pools at condominium associations, and front door locks. In some cases, locks are used hundreds of times a day. Below is a picture comparing a worn cylinder with a new cylinder. Notice the size of the keyway in the worn cylinder and the open rectangular shape.
