Basics of Architectural Hardware

LOCK IT

All locks are not created equal. They come in many types, designed to perform a range of functions and provide different levels of security. While their primary purpose is always security, locking needs will vary between a storage closet and a building entrance.

Types of Locks

The main types of locks used commercially include mortise, cylindrical, and rim. These designations are based on the design of the lock, how and where it engages, and how it is mounted to the door.

Mortise locks are generally considered the heaviest duty products in the marketplace. They are typically used in area of high traffic or heavy commercial usage, where greater security is required. A mortise lock is installed in a mortised pocket in the door, with the housing of the lock contained in the door. The cylinder is screwed through the skin of the door directly into the metal lock case, with only the cylinder head and spin ring projecting from the face of the door. The lock case may contain a dead bolt as well as the normal dead latch for added strength and security.

Cylindrical locks are a simpler design installed in two intersecting holes in the door. Normally a 2-1/8" hole through the face of the door intersects either a 7/8" or 1" diameter hole from the edge. The cylinder is contained in the outside knob or lever, away from the surface of the door.

Rim locks are mounted to the inside surface of the door, with a cylinder installed on the outside surface in a hole bored through the door. They typically have either a spring latch or dead bolt operation, engaging a strike mounted to the frame around the door. There are several types of dead bolt mechanisms found on rim locks.

Lock cylinders in these and all locks may be designed for standard keys readily available at local hardware stores or controlled access/high security keys, which are available only from the manufacturer and selected locksmiths.

There are other mechanisms that can be considered under locks, such as hospital latches and exit devices. These are all useful varieties with specific purposes or applications, and for this article they will be considered from the standpoint of lock function as variations in trim. Other lock varieties, such as cabinet locks and padlocks, will not be discussed.

Most electrical and electrified products are actually electrically operated mechanical locks and also will not be explored in further detail here. These include electromagnetic locks, alarmed or delayed exit devices, electric latch releases, auxiliary alarm locks, touch keys, card readers, keypads and other electrified means of activating or controlling a lock. In most cases, the outside lever is unlocked by a solenoid instead of a key, although a key can provide an override or safety feature. The main benefit of electronic access control is a more flexible and higher level of key control than the typical mechanical key system.

Lock Functions

Not all locks function the same way. Commercial cylindrical and mortise locks may have several different functions to suit almost every combination of convenience and security requirements. The most common include passage, privacy, office, entry, classroom, and storeroom, named after their most typical applications.

Passage sets are not locks in the true sense of the word, but incorporate a lever or knob on either side of the door and a latch to hold the door shut. There is no provision for a key, as no lock cylinder is included.

Privacy locks are the type used in a public restroom, or perhaps a residential bedroom or bathroom. They contain no cylinder and do not have a key. However, they can be locked from the inside for privacy, usually by a pushbutton built into the knob or lever. They generally include a provision for emergency access from the outside, often using a small screwdriver or pin to unlock the outside knob or lever through a hole in the trim. Hospital privacy latches have thumb turns on both sides so a nurse or attendant can gain entry to a patient's bathroom quickly in an emergency.

Office locks are locked from the inside by a pushbutton. The outside lever or knob remains locked until unlocked with a key from the outside or by rotating the inside lever trim. The inside knob or lever is always free for immediate exit.

Entrance or entry locks maybe locked by pushing and turning a button and are unlocked by key until the inside button is manually unlocked. They are also available with pushbutton locking, in which pushing the button locks the outside knob or lever until it is unlocked by key or by turning the inside knob or lever. The inside knob or lever is always free for immediate exit.

Classroom locks(maintained)are always locked and unlocked from the outside by key. The inside knob or lever is always free for immediate exit.

Storeroom locks (momentary) have a fixed outside knob or lever, and the latch is retracted by the key from the outside. The inside knob or lever is always free for immediate exit.

Making the Grade

Locks are available in different grades, which relate to their construction and durability. These grades are a measure of application suitability. Most commercial applications require either Grade 1 or Grade 2 locking products. Because security, protection from vandalism, durability under heavy usage and other considerations are important, the greater strength of Grade 1 locks makes them the suitable choice for demanding applications. Grade 2 products are adequate for lighter duty, such as storage closets or doors where security is less of an issue than simply excluding people in general. They will keep people from walking through a door, but they provide much less protection against deliberate force than Grade 1 products.

ANSI/NHMA standards, monitored by independent testing laboratories, separate Grade 1 from Grade 2. Typically, Grade 1 locks must meet twice the requirements of Grade 2. In cycle tests for example, a Grade 2 lock need only function for 400,000 cycles, while a Grade 1 lock must meet at least 800,000 cycles. Some manufacturers regularly test beyond that limit into the millions of cycles.

Even among locks promoted as Grade 1, there can be some differences. For mortise locks, ANSI A156.13 makes distinctions between Grade 1 Operational and Grade 1 Security. The section includes a distinct operational test that encompasses everything from cycling to finish testing of mortise locks. A separate listing covers security grading.

When choosing a Grade 1 mortise lock, it is important to know whether the rating given is for security, operational or both. Sometimes, the higher rating is available only as an expensive up-charge. A lock with concealed cylinder trim may be Grade 1 operational and Grade 1 security, while one with an exposed cylinder may be only Grade 2 security. One of the most difficult requirements to meet for Grade 1 security is a cylinder wrenching requirement, in which a cylinder must withstand (120 ft. lbs) of torque. Here, a weak point of many mortise lock designs is the cylinder attachment to the lock case. The screw that fits into a groove on the side of the cylinder will either bend or cut a groove in the cylinder body and allow the cylinder to be threaded out. Another security test is a 3,600 lb. pull test applied to the cylinder. A concealed cylinder cannot be accessed for these

For most other types of locks, both security and operational aspects are included under a single grade. ANSI A156.2 Series 4000 is the standard for bored-in locks and latches. While only an operational grade, it includes some considerations such as lock lever torque, vertical impact load on the knob or lever, and other destructive tests. Because the cylinder projects from the door, it is more vulnerable to attack than a mortise lock and is not really considered a security item.

Unlike some other hardware, which is available in listed and non-listed versions, most commercial locks are UL fire-listed. Most manufacturers have different latch bolt lengths available and have listed them so they can be used on both fire-rated and non-fire-rated doors. However, different products are listed with different sizes of door, depending on such variables as latch type and size. When used in a fire-rated application, each product should be checked in the UL Building Materials Directory to see what its listing actually covers.

What Type to Use?

Typical products available as Grade 1 include cylindrical key and lever locks, mortise locks, heavy-duty mortise, auxiliary deadbolts, and the locks used with electronic or other access control hardware.

For most high-traffic areas, such as schools, heavily used offices, stores or other public buildings, a Grade 1 mortise lock is preferred. Because its case is much larger than that of a cylindrical lock, it can be built to incorporate parts with thicker cross-sections and greater strength.

An alternative would be a Grade 1 cylindrical key and lever lock, which is probably the most popular for retrofitting because little or no additional prep is required. For example, converting from a cylindrical knob set to a lever in order to meet ADA requirements usually entails drilling only two holes. To achieve higher security where heavy use or abuse is expected, combine the Grade 1 cylinder lock with an auxiliary deadbolt, providing this combination is allowed by the local building codes.

An advantage of a mortise lock in these situations is that mortise locks are available with a deadbolt as an integral part of the lock case. This combines security with ease of operation, because of dual retraction. From the inside, when the door is locked and the deadbolt is extended, simply operating the lever retracts both the latch bolt and deadbolt simultaneously. From the outside, the key will open both in sequence, retracting first the deadbolt and then the latch bolt as the key is rotated further.

The trim used with a lock should be built as strong as the rest of the lock. Lever trim, which is becoming universal because it meets ADA requirements and is easier for people to use, is also subject to a wide variety of constructions and strengths. Mortise locks typically use either forged or cast levers, both of which are quite strong.

Whatever type of lock the application requires, it is sure to be available from the wide variety of types now on the market. A suitable choice will consider the requirements for security, durability, usage demands, building codes and accessibility needs.