Cylindrical locks are perhaps the most popular kind of lock. They are widely used in both commercial and residential applications. The term 'cylindrical' describes the shape of the lock chassis.

Keyed cylindrical locks are easy to identify. Looking at the door from the key side, a person can easily see that the keyhole is located in the lever or knob as opposed to above the lock. That is why cylindrical locks are also often called "key in lever" or "key in knob" locks.

Because of the American Disabilities Act (ADA), commercial applicatons almost always require levers. Levers can also be used in residential applications. Knobs are used almost exclusively in residential applications.

Cylindrical locks are graded for various applications by ANSI.

• ANSI Grade 1 cylindrical locks are for use in high traffic and/or high abuse applications such as high rise office or residential buildings, factories, warehouses, retail stores and schools.
• ANSI Grade 2 cylindrical locks are for use primarily in light commercial applications such as small offices or in residential applications.
• ANSI Grade 3 cylindrical locks are used mainly in residential applications.

Above is an illustration detailing the major components that make up a cylindrical lockset. Knowing the names of these components is helpful when speaking to your security professional.

Lock function describes the way a lock works. Below are listed a few common cylindrical Lock functions. Most commercial grade cylindrical lock functions have ANSI number designations which I have included. To simplify the descriptions I will refer to both knobs and levers as 'handles'.

Non-Keyed Functions

• Passage - ANSI F75

• Both inside and outside handles always unlocked.

• Privacy ANSI F76

• Both inside and outside handles unlocked unless outside handle is locked by pushing button on inside handle. Outside handle unlocked by closing door, turning inside handle, or outside emergency turn slot.

Keyed Functions

• Entry ANSI F82

• Button on inside handle locks outside handle. Pushing button allows outside lever to be unlocked by turning inside handle or outside key; pushing and turning button clockwise causes outside handle to remain locked until button is turned counterclockwise and inside handle is turned. Inside handle always unlocked. When outside lever is locked, key retracts latch.

• Storeroom ANSI F86

• Outside handle always locked. Key retracts latch. Inside handle always unlocked.

• Classroom ANSI F84

• Inside handle always unlocked. Outside handle locked and unlocked by key in outside handle.

Electromechanical Cylindrical Locks:

• Fail Safe

• Outside handle locked when power is on. Key retracts latch.

• Fail Secure

• Outside handle locked with power is off. Key retracts latch.

Types of Latches

Below is an illustration of the deadlatch belonging to a cylindrical lock. Notice the auxiliary deadlatch, or deadlocking feature. Used mainly on keyed functions, the auxiliary deadlatch remains depressed when the main latch extends into the strike plate, activating a deadlocking feature within the latch that inhibits shimming or jimmying the deadlatch.

Deadlatches are usually (but not always) used with keyed functions. Non-keyed functions such as privacy and passage sets use spring latches, which have no auxiliary deadlatch.

At right is shown the door prep for a standard cylindrical lock. The "bore" is a 2-1/8" hole drilled through the face of the door. The "cross-bore" is a hole drilled from the edge of the door into the bore at the centerline. The edge of the door is mortised, stamped or machined to accomodate the latch face. The distance from the edge of the door to the centerline of the bore is called the "backset". Typical backset for a commercial application cylindrical lock is 2-3/4 inches.

Notice the through-bolt holes above and below the bore. Grade 1 cylindrical levers almost always have through-bolts outside the bore, while Grade 2 levers sometimes do and Grade 3 levers hardly ever have them.