This article takes an in depth look at locks and their use.
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A lock is a device that secures an opening by engaging a latch, solid cylinder, bolt, or similar metal plunger into a strike plate. These metal mechanisms are used to restrict access for privacy, security, or safety purposes. The lock mechanism controls the movement of the latch, bolt, or shackle, either holding it in place or retracting it to open the lock.
The term "lock" refers to a variety of devices used for added security, including padlocks, combination locks, door locks, deadbolts, restraining bolts, electric locks, and key locks. The lock mechanism encompasses the internal structure of the lock, which may be warded, pin tumbler, spindle, or disk tumbler. Lock mechanisms can be classified as key-operated, combination, or electric.
Historically, all locks were mechanical, utilizing levers, wheels, gears, and cams. In the past century, locks have evolved to incorporate sophisticated programming, electronic mechanisms, and various automatic locking methods.
Locks serve a common purpose: securing items or areas. They are available in various designs, forms, and configurations tailored to specific applications, and must be installed carefully to ensure optimal performance and efficiency. The security grade of a lock is largely determined by the materials used; low-security locks are typically made from inexpensive materials and mass-produced, while high-security locks use premium materials and are built to stricter standards.
Special-purpose locks are designed with a thorough understanding of their intended application. They are crafted from high-quality materials to provide a secure and precise fit. Unlike standard locks from home improvement stores, high-security locks must adhere to rigorous standards and are engineered to withstand demanding conditions.
Key locks are constructed using various metals: brass and zinc are typically used for the internal mechanism, while steel is employed for the cam that extends into the door frame's strike plate. The outer casing of the lock may be made from materials such as brass, chrome, steel, nickel, or their alloys.
In standard tumbler key locks, the key is crafted first. It features five high points cut at different levels, with each level identified by numbers ranging from one to seven. A typical five-tumbler lock offers 1024 possible combinations of levels. The pins inside the key mechanism align with these key levels, allowing rotation only with the correct key. Pins obstruct keys with incorrect levels, as illustrated in the diagram below.
The most challenging aspect of manufacturing a key lock is the precision required for the pins, which must have tolerances within ±0.001 inch. In the image below, you can see the small pins resting on the key’s teeth, with a second set of pins and springs positioned above. The pins feature notches below their tops that must be meticulously machined.
The key cylinder is the component where the key is inserted to move the pins and retract the plunger from the strike plate. It constitutes the main body of the lock and is round in rotational locks.
The part of the lock that engages with the strike plate is referred to by various names, including latch, bolt, or plunger, depending on the manufacturer and lock design. This component extends into the door frame and must align precisely with the strike plate for secure operation. The latch on the deadbolt key lock shown below is visible on the left side of the image.
The strike plate is where the plunger or bolt fits into the door frame. It is mounted on the door frame and varies in design based on the required security level. Made from heavy-duty metal, strike plates are robust and resistant to removal. Some strike plates include additional security features to prevent the bolt from being retracted without engaging the lock.
The earliest type of key lock was the warded lock, also known as a ward lock, which used obstructions called wards. The key for a ward lock has cutouts that pass through the wards. For enhanced security, ward locks can be highly complex, making unauthorized access difficult. The key type used in ward locks is shown in the diagram below.
To bypass ward locks, a skeleton key with a single cutout can be used to navigate all the wards.
Combination locks are operated by aligning a series of discs in a specific sequence. Most common combination locks use an internal mechanism with interconnected discs. To unlock, the discs rotate and align with preprogrammed notches or positions. These discs are separated by nylon or plastic spacers, allowing them to turn independently. Each number on the dial corresponds to a wheel or disc.
Combination locks come in two types: keyed and manual. Keyed combination locks require entering a sequence of numbers using a keypad on the lock’s face, while manual combination locks operate similarly to dial locks. The internal mechanisms of both types resemble those found in padlocks or traditional combination locks.
Combination locks are made from corrosion- and rust-resistant materials like plated or coated cold-rolled steel or stainless steel, ensuring durability and longevity without frequent repairs or replacements.
The lock case of a combination lock encases the mechanism, shielding it from damage and environmental factors. It is typically constructed from robust metals, including various steel alloys.
Keyless combination locks can feature either a dial or thumb screws to align the discs. Dial combination locks are numbered from 1 to 59. Selecting a number on the dial aligns the discs to unlock the mechanism.
The dial rotates a shaft or spindle on which the discs are mounted. This rotation functions similarly to turning a key, aligning the discs instead of pins. As the dial and shaft rotate, the discs align according to the selected number on the dial.
In high-security combination locks, a fence attached to a lever is positioned above the discs or wheels. This fence prevents the door from opening unless the correct combination is entered. When the correct sequence is dialed and the discs align, the fence drops into a slot created by the aligned discs, allowing the door handle to turn.
Electric door locks offer an advanced method of automating the process of locking and unlocking doors, enhancing security and eliminating the need for traditional keys. These locks can be controlled remotely via a phone, laptop, or other electronic devices, providing added convenience and modern security features.
Electric locks typically draw power through the door and frame to connect with the power supply and access control system. Some electric locks are self-contained, using a replaceable battery rather than needing a direct connection to a power source.
Electric locks can be designed similarly to traditional locks, with plungers, latches, or bolts activated by an electrical system. They function on the principle of a solenoid, which, when energized, pushes the plunger into the strike plate. Additionally, there are magnetic electric locks that use a magnet mounted on the door frame and a metal plate on the door to secure it with substantial force. However, a drawback of magnetic locks is that once the magnet is deactivated, the door becomes unsecured.
Deadbolts require manual operation to lock and unlock, offering enhanced security and durability compared to other types of locks. They feature a robust metal bolt that extends into a deep strike plate on the door frame, making them more resistant to forced entry.
There are several types of deadbolts: single cylinder, double cylinder, one-sided, and keypad. Single cylinder deadbolts have a key slot on the exterior and a turning mechanism on the interior. Double cylinder deadbolts have key slots on both sides, providing added security. One-sided deadbolts can only be locked from one side of the door. Keypad deadbolts feature a numerical keypad for code entry, eliminating the need for a physical key.
The variety of locks available is vast, catering to different levels of security needs. Ranging from simple locks used for securing cabinets to sophisticated systems designed to secure high-value assets or imprison individuals, the range of locks is extensive. Common household locks are readily available online or at home improvement stores, but specialty locks tailored for high-security applications are often custom-designed and not widely available through standard retail channels.
Within household locks, the level of security can vary based on the quality of materials used in their construction. Additionally, both household and high-security locks might be chosen for their appearance, depending on their intended location and use.
Even the most comprehensive catalog of locks will not encompass every type, as new designs, security features, and applications are continuously being developed and introduced.
As with all forms of locks, there are many different types of cabinet locks for securing cabinet doors. A few of the common types of cabinet locks are magnetic and latch for home cabinets. More secure forms for cabinet locks are available for business cabinets that have bolts, cylinders, combinations, and latches. Each of these are designed for a specific application and level of security.
Latch cabinet locks utilize a latch and catch mechanism to keep the cabinet door securely closed. In some designs, the catch is mounted on the frame inside the cabinet door, while other variations use magnets and tabs for secure closure.
Magnetic cabinet locks use magnets to secure the cabinet door. A magnet is fixed to the cabinet frame, while a metal plate is attached to the door. When the door is closed, the metal plate is drawn towards the magnet, keeping the door shut. These locks can be easily opened by pulling the cabinet door handle.
Cam cabinet locks offer a discreet locking solution that does not alter the appearance of a cabinet. These cylindrical locks are particularly suited for wooden cabinets. They feature a metal tube with a side hole that engages with the bolt's tongue. Cam locks can be installed in various locations on a cabinet, including joints, and are almost invisible once the cabinet is fully assembled.
Double door cabinet locks feature an active door and a fixed door, with the fixed door being secured to the active door when closed. The active door is equipped with a cam lock or another keyed locking mechanism. When unlocking the cabinet, the key unlocks the active door, while the fixed door can be opened by hand.
Another type of double cabinet lock uses a single key to operate two bolts. Turning the key causes both plungers or bolts to engage with the strike, locking both doors simultaneously, as shown in the image below on the left.
Push cabinet locks are mounted on the interior of a cabinet door. They consist of a single bracket with a shaft and ball that connects to a catch. The catch features a clasp that grips the ball when it is pressed into place. This mechanism keeps the cabinet door securely closed until a slight force is used to disengage the ball bracket from the catch.
Cam locks feature a metal plate, or cam, located beneath the locking mechanism. When a key is inserted and turned 90°, the cam secures the frame and the door. There are two main types of cam locks: standard and tubular. Standard cam locks operate like conventional pin tumbler locks, while tubular cam locks use a horizontal pin system.
Cam locks are valued for their cost-effectiveness and practicality, making them a popular choice for securing cabinets, desk drawers, filing cabinets, vending machines, mailboxes, and cash boxes. They are suitable for commercial, residential, and industrial settings.
The core component of a cylinder lock is its cylinder. When the key is inserted and the cylinder is turned, the cam draws the bolt back, allowing the door to open. Turning the cylinder in the opposite direction causes the cam to release the bolt, locking the door securely.
A cylinder lock has a pin and tumbler design where the key aligns the pins to move the cam and bolt. The pins are in pairs positioned along the length of the cylinder and rest on the bottom of the cylinder when no key is inserted. The pins are positioned one on top of the other with a spring located above them. When the proper key is inserted and turned, it pushes the pins upward. The image below shows a cross section of a cylinder lock with the positioning of the pins and cam.
The term "door lock" encompasses a wide range of mechanisms designed to restrict entry or access. These devices use latches, bolts, or plungers mounted in the door to establish a secure connection between the door and its frame. Depending on their design and function, door locks can be mechanical, magnetic, electronic, or automated.
A standard door lock is a crucial element in any construction project, offering safety, protection, and control over access to buildings or cabinets. The type of door lock chosen depends on the required security level, which can vary from residential homes to vaults or private enclosures.
Biometric locks represent a high-security solution designed for applications requiring stringent access control. They utilize physical credentials such as fingerprints, retina scans, or voice recognition to permit entry. These locks are resistant to hacking or picking, providing superior security.
Keyless locks utilize a keypad that requires entering a code to disengage the locking mechanism. Often known as smart locks, these advanced devices are programmable and may feature automatic functions along with WiFi and app integration. Keyless locks eliminate the need for physical keys and offer enhanced security, as they are resistant to picking or other forms of circumvention, apart from brute force attacks.
The access code for a keyless lock can be easily modified to suit different needs, such as granting temporary access to a house sitter or assigning unique codes for various users in a home or office. These locks are powered by batteries, including 9V, AA, and AAA types, which can be replaced quickly to ensure reliable operation.
Although keyless locks are advertised as not requiring a key, some forms come with a key backup for special situations or when the battery is dead. Additionally, keyless locks can be programmed to lock after a preset period of time. They are backlit for easy visibility in darkness or low light conditions.
A mortise lock is fitted within a door and requires carving a specific pocket or shape into the door. Unlike cylindrical locks, which necessitate a hole drilled all the way through the door, mortise locks are installed into a pocket cut into the edge of the door. An example of a mortise lock installation can be seen in the image below.
To unlock a mortise door, turning a handle or knob connected to a spindle disengages the bolt from the strike plate on the door frame, which holds the locking and latch bolts. When a key is inserted and turned, it rotates the cylinder to retract the latch.
Mortise locks differ from standard cylindrical locks and feature distinct components including the lock body, knob, spindle, cylinder, and strike plate.
Mortice locks are widely used for their strength, durability, and reliability. They are built with solid metal components and large springs, making them capable of withstanding constant use and abuse.
OEM manufacturers produce locks for other companies to be marketed under their brand names, leveraging their ability to produce at lower costs. OEM locks include a variety of types, such as cam locks, vending locks, padlocks, parking meter locks, cabinet locks, switch locks, and electronic locks, all made to the specifications of the purchasing company.
Utilizing OEM manufacturers allows companies to expand operations without increasing labor, space, or facilities. OEMs provide high-quality locks at reduced costs, enabling companies to offer competitive prices. With OEM locks, a wide range of keys and code combinations can be created to ensure security, safety, and reliability.
Additionally, OEM companies use high quality raw materials that relieves the marketing company of another expense. Locks are produced to meet the exact design of the marketing company as well as its quality. OEM locks have several different key types and combinations, which further increases their security and safety.
Tubular locks, also referred to as radial or circle pin tumbler locks, are distinguished by their round keyhole design. Sometimes called Ace locks, named after the company that introduced them, these locks feature a circular keyway with a central cylindrical component.
Inside the tubular lock, there are typically six to eight pins, with seven or eight being most common. Unlike cylinder locks where the pins are aligned vertically, tubular locks have horizontally oriented pins. The lock's plug accommodates both the pins and the driver pins along with their respective springs.
The key used for tubular locks is circular and features a central hole with outer grooves. To correctly insert the key, a notch on it must align with a corresponding notch in the keyway. As the key is inserted, it moves the pins to engage or disengage the lock.
The diagram below demonstrates how the pins and their springs are arranged horizontally within the lock when the key is inserted.
Vending machine locks generally fall under the category of tubular locks and are designed with high durability to resist tampering and theft. These locks are crucial for securing various valuable devices and machines, such as pay phones, ATMs, and computers. They are typically constructed from robust materials like hardened steel or stainless steel to ensure maximum protection.
Given their widespread use, vending machine locks are coated to guard against corrosion, rust, and tampering. Their cylindrical key design enhances security by making them challenging to pick. Additionally, tubular locks offer a cost-effective alternative to traditional cylinder locks while delivering comparable security and durability.
Aside from tubular locks, vending machine locks can have the same standard deadbolt designs, combination, and spring latch locks. Many vending machine manufacturers have the locks for their machines custom made as an extra level of security.
Euro cylinder locks, sometimes called barrel locks, profile cylinder locks, or pin tumbler locks, are widely used across Europe due to their simplicity in installation and replacement. These locks feature a keyhole at both ends, allowing them to be operated from either side of the door. Often referred to as double key locks, they require a key to unlock from both sides. If a key is left in one side, it will block access from the other side. Their versatility and compatibility with deadbolts contribute to their widespread use and popularity.
One crucial aspect in choosing a lock is the material from which it is made. Typically, locks are crafted from steel or stainless steel because of their robustness, longevity, and capacity to endure frequent use. The choice of material significantly impacts the lock's price, with copper being a high-quality yet costly option.
The durability and effectiveness of a lock are closely linked to the metal used in its construction. Locks available at general home improvement stores are often mass-produced and lack the advanced security features found in biometric or other high-security locks.
As with most applications, stainless steel is the number one choice for manufacturing locks due to its exceptional durability and corrosion resistance. The bright shine of stainless steel never fades and is available in a wide range of grades to fit the many varieties of locks. Austenitic grades of stainless steel never rust but are non-magnetic.
Copper is frequently utilized in lock manufacturing because of its superior mechanical qualities, resistance to corrosion and rust, and ease of processing. Additionally, copper's aesthetic appeal makes it ideal for handles and decorative elements of locks. Its smooth surface, uniform density, and absence of pores or voids enhance its suitability for these applications.
Although zinc is not commonly used for the primary construction of locks, it is well-suited for crafting intricate and detailed components. Its use in locks is primarily for aesthetic purposes, as it provides a high-quality finish and decorative appeal.
Steel comes in various grades, giving lock manufacturers the flexibility to select the appropriate type for their needs. Known for its exceptional strength, durability, and toughness, steel is a preferred material for producing lock components. However, its utilitarian appearance makes it less suitable for decorative purposes.
To enhance the longevity and effectiveness of locks, their metals are often treated with protective coatings through electroplating, coating, or chemical oxidation. These surface treatments are designed to prevent corrosion, improve aesthetics, and boost durability. Quality control measures for these coatings include tests for thickness, adhesion, resistance to salt spray, and moisture protection.
Among the various aspects of coating, appearance is particularly important. A well-applied coating not only protects the lock but also enhances its visual appeal, which is especially important if the lock is in a prominent location.
Selecting the appropriate lock can be complex, especially when it plays a crucial role in the security of a location. Locksmiths often evaluate multiple factors to determine the most suitable lock for each specific application.
Locks primarily serve to provide privacy, security, control access, and ensure smooth operation. The intended location for the lock significantly influences its quality and type. For instance, ease of use may be particularly important for elderly or disabled individuals.
The durability required for a lock largely depends on its location and frequency of use. Locks for storage rooms, secure cabinets, or commercial entrances need to be more robust compared to those used infrequently, such as on a residential entry door.
Locks are categorized into ANSI grades 1 and 2. Grade 1 locks offer the highest level of durability and are suitable for high-traffic areas, enduring extensive use. Grade 2 locks are also suitable for commercial use but are designed for locations with less demanding traffic.
The visual appeal of a lock is influenced by its placement. There are numerous styles, sizes, finishes, and mechanisms available to ensure the lock complements its setting.
While cost is a consideration, it is often less critical than functionality. Opting for a cheaper lock made from lower-quality materials can lead to problems. The key factor should be how well the lock performs its intended function, as a less expensive lock protecting valuable items might ultimately be more costly.
The effectiveness of a high-quality lock can be compromised by a poorly constructed door. Doors with hollow cores or weak frames are likely to fail before the lock does, making the door’s quality essential.
Compliance with building codes and fire safety regulations is important when selecting locks. Locks requiring keys on both sides are generally considered unsafe. Look for locks that meet Underwriter Laboratories (UL) standards for fire safety, which will be indicated on the packaging.
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