Cylindrical Locks: The Bored Lockset Behind Most Knobs and Levers

How a Cylindrical Lock Works

The standard for bored locks, ANSI/BHMA A156.2, defines a bored lock as "a lock installed in a round bored opening in the edge and face of a door." Allegion describes a cylindrical lock more specifically as a bored lockset "whose latch or bolt locking mechanism is contained in the portion installed through the cross-bore."

The main parts:

• Chassis: the round housing in the cross bore that holds the locking mechanism.
• Latch: a spring latch or deadlocking latch installed through the edge bore. It engages the chassis and projects into the strike on the frame.
• Trim: the outside and inside knobs or levers, with roses covering the bore.
• Cylinder: on keyed functions, a key cylinder in the outside knob or lever (sometimes an interchangeable core).
• Locking control: on the inside, a push button, turn button, or second cylinder, depending on the lock function.

Turning either lever retracts the latch. When the outside trim is locked, the outside lever will not retract the latch, and only the key or the inside lever does. The same architecture supports passage, privacy, storeroom, classroom, and many other functions.

Door Preparation

Schlage's ND Series catalog says the ND line uses "an ANSI door prep common across cylindrical locks." Schlage's ND installation template shows that prep as a 2-1/8" cross bore and a 1" edge bore, at a standard 2-3/4" backset. The backset is the distance from the door edge to the center of the cross bore, and the catalog also lists latches for 2-3/8" and 3-3/4" backsets. The same catalog says all ND latches have a 1/2" throw except an anti-friction fire door latch with a 3/4" throw, and its default strike is an ANSI strike measuring 1-1/4" × 4-7/8".

Other products and doors can differ, so the manufacturer's template for the specific lock governs.

Knobs, Levers, and Roses

Knob sets and lever sets share the bored format but behave differently. A lever sticks out to one side, so it needs a spring cage to return it to horizontal. Allegion notes that these spring cages lead to a bigger rose, typically around 3.5 inches in diameter, while knob roses are usually around 2.5 inches.

Levers also matter for accessibility. BHMA's A156.2-2022 summary notes that ADA and A117.1 require operable parts to be "operable with one hand and shall not require tight grasping, pinching or twisting of the wrist." Lever or paddle trim meets those stipulations, while BHMA says knob trim should be avoided where they apply. Local code and the authority having jurisdiction (AHJ) decide where accessible hardware is required.

Cylindrical vs. Mortise vs. Tubular

Two naming cautions:

• "Tubular lock" means two different things. A tubular lockset is a bored lock with a center spindle through the lock body and latch. A tubular key lock is the circular-key pin tumbler used on vending machines; see tubular locks. They are unrelated mechanisms.
• "Cylinder" vs. "cylindrical." Many keyed locks contain a key cylinder. "Cylindrical lock" names the bored lockset format, not the key mechanism inside it.

Standards and Grades

Commercial cylindrical locks are tested to ANSI/BHMA A156.2 (Bored and Preassembled Locks and Latches). The standard includes cycle, strength, operational, material evaluation, finish, and dimensional criteria across three grades. BHMA's highlight page for A156.2-2022 says:

• Grade 1 locks must pass one million cycles with a 10-pound axial load.
• Lever-operated locks must open with a maximum torque of 28 in-lbf.
• Security testing includes a 1,200 in-lbf locked-lever torque test.

Older editions used different figures. Allegion's knowledge base lists 800,000 cycles for Grade 1 under A156.2-2003, so name the edition when comparing claims. See ANSI/BHMA lock grades for how grades differ between product standards.

Residential bored locksets can instead be certified to ANSI/BHMA A156.39 (current edition 2025), which uses Grades A, B, and C. BHMA's summary says Grade A locks must pass 400,000 cycles with a 5-pound axial load.

Fire-rated doors need hardware listed for that use. BHMA notes that hardware for fire doors is evaluated and listed to UL 10C by an accredited third-party testing laboratory. Allegion's knowledge base shows Schlage cylindrical series with UL listings for 3-hour fire doors. Whether a particular lock may be used on a particular fire door depends on its listing and the AHJ.

What Early Patents Show

The bored format is closely tied to Walter R. Schlage, and his patents on Google Patents record the design goals in his own words:

• U.S. Patent 1,456,041, "Door lock." Filed April 12, 1920, and granted May 22, 1923, it was assigned to Schlage Manufacturing Company of San Francisco. Its stated objects include a "cheaply manufactured" lock with "a unit housing which contains the entire lock mechanism" that "may be readily installed without cutting away an excess of the woodwork." It also names "a lock housing which is cylindrical in cross section."
• U.S. Patent 1,489,675, "Door lock." Filed October 5, 1920, and granted April 8, 1924, also assigned to Schlage Manufacturing Company. It describes a locking mechanism placed in the spindle and "actuated by a push button carried by the inner knob." The lock "is locked by the mere depression of the push button" and restored to unlocked by turning the inner knob.
• U.S. Patent 1,674,841, "Door lock." Filed August 20, 1923, and granted June 26, 1928. Its stated object is to "improve and simplify the construction of door latches to permit saving both in time and cost of installation," using a latch made of two separable, self-contained units.

The push-button idea in the 1924 patent survives in the privacy functions of many current cylindrical locksets; see lock functions.

Related Topics

• Mortise locks: the pocket-mounted alternative
• Lock functions: passage, privacy, storeroom, classroom
• Door latches: deadlocking latches and strikes
• Strike plates: the frame side of the latch
• ANSI/BHMA lock grades: A156.2 vs. deadbolt standards
• Deadbolts: the auxiliary lock often paired with a cylindrical lockset
• Interchangeable cores: removable cores used in many commercial cylindrical locks

Sources