This article takes an in depth look at continuous hinges.
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A continuous hinge is a long, single-piece hinge that covers the entire length of a door, cabinet, lid, or enclosure. Made from materials such as nickel, brass, aluminum, steel, and stainless steel, these hinges are custom-cut to match the dimensions of the opening. Like smaller hinges, continuous hinges may come with pre-drilled holes for straightforward installation, though versions without pre-drilled holes are also available.
The original continuous hinges were made to hold the lid of grand pianos, which gave the hinges the name "piano hinges." As other uses for piano hinges were discovered, the more general name of continuous hinge became popular.
Over time, piano hinges have evolved into continuous hinges, designed for various applications and configurations. These hinges are available in standard lengths of six and eight feet, with options in different thicknesses, pin diameters, widths, and finishes. Their durability makes them ideal for applications that endure frequent use and substantial wear.
Over the years, piano hinges have changed and developed into continuous hinges for use in a wide range of applications and multiple configurations. They are manufactured in standard lengths of six and eight feet and come in different thicknesses, pin diameters, widths, and finishes. The durability of continuous hinges makes them perfect for applications that experience extensive use and intense wear.
Throughout the evolution of the piano, from its early forms like the monochord to the clavichord, harpsichord, and finally to the modern pianoforte, numerous innovations have shaped its current design. One key challenge was finding a solution for supporting the cover or lid that protects the instrument's major components.
In the earliest pianos, the cover was not a significant issue. However, with the development of the harpsichord, a practical method for opening and closing the lid became necessary, as manually lifting it for performances was impractical. This led to the invention of a hinge that could hold the lid in place, allowing the sound board and strings to be exposed while maintaining their resonance.
Designers and craftsmen were tasked with creating a hinge that spanned the full length of the lid, supporting it effectively without obstructing or muffling the instrument's sound. The hinge needed to be robust enough to handle the weight of the open lid.
Early piano hinges were meticulously designed and crafted to match the dimensions of the piano lid's long edge, with adjacent or staggered holes. Craftsmen shaped the metal by hand, incorporating a barrel for the pin, which was a long, continuous solid metal dowel.
As piano hinges gained popularity beyond their initial use on piano lids, manufacturers sought faster and more economical production methods. This led to a continuous process where two steel pieces were fed through a machine, with the long pin or dowel positioned between them. The knuckles were then formed over the pin, uniting the steel pieces to create the hinge. This method is still in use today.
The production of piano hinges is streamlined by feeding material continuously into the forming machine. This process enables the placement of various hole shapes and cutting of hinges to different lengths. A piano hinge is measured by its open width across both leaves, the diameter of the pin running the length of the hinge, and the thickness of the leaves.
The traditional piano hinge has evolved to become an essential component for securing doors and openings in cabinets and enclosures. Originally designed for pianos, its application has broadened significantly, leading to the development of heavier, more durable, and varied versions of the hinge. This evolution has given rise to three different names for the piano hinge.
Though the term piano hinge harkens back to the development of the first hinge for piano lids, it is still used today by hinge manufacturers to distinguish piano hinges from barrel, butt, butterfly, flush, knife, mortise, offset, pivot, soft close, spring, and strap hinges. One of the names that has stuck with piano hinges is continuous, which is a description of the process used to produce piano hinges.
While "continuous hinge" is often used interchangeably with "piano hinge," some manufacturers maintain the original term by calling it a continuous piano hinge to emphasize its historical design.
The classic piano hinge featured two leaves with curled knuckles connected by a long pin or dowel. This design is still in use today but represents just one of the many types of continuous piano hinges available.
In the past, craftsmen shaped the original piano hinges from basic metals. Today, however, the materials used have expanded beyond these early metals to include advanced and diverse materials such as plastics and fabrics. Modern continuous hinges are distinguished from their traditional counterparts by the use of these newer materials, reflecting the advancements and changes in hinge design since the original piano hinge was introduced.
Hinges are available in numerous sizes, types, and designs, catering to a range of needs from small jewelry boxes to large vault doors. Each type is crafted to serve specific functions and accommodate various requirements, including different lengths, styles, sizes, strengths, and aesthetic preferences. Among the diverse hinge styles, continuous hinges are notable for their durability, ease of alignment, smooth operation, and cost-effectiveness.
Continuous hinges are constructed from a range of materials such as steel, stainless steel, aluminum, nickel, brass, plastics, and fiber. They are available in various grades suitable for commercial, residential, heavy-duty, military, and marine applications.
Carbon-Kevlar continuous hinges are constructed from carbon fiber and feature a flexible gap between the wings. Unlike traditional gear, pin-and-barrel, or pin-and-barrel plastic hinges, these hinges are a single unit with a flexible section between the wings that functions similarly to a pin in a barrel. This flexible component is made of woven Kevlar with urethane injected into it.
Like other continuous hinges, carbon-Kevlar hinges are available in various sizes and can be found as heavy-duty models with a double layer of Kevlar.
Friction continuous hinges, also known as torque hinges, use internal friction to be held in position. When a door or lid is opened, the hinge keeps the door of the application in a set position, preventing it from accidentally closing. Friction continuous hinges are designed in accordance with the axial and radial tensile load strength necessary to support a lid or door and hold it in position.
The image below illustrates how the knuckles fit together closely.
Geared continuous hinges are engineered for environments with heavy traffic, such as retail stores, commercial establishments, and office buildings. These hinges feature interlocking gears housed under a protective cap, extending the full length of the hinge. Given their demanding applications, geared continuous hinges are constructed from robust, durable materials designed to withstand significant wear and tear.
Various types of geared continuous hinges exist, but they all share the common characteristic of having their gears enclosed within a concealed leaf, akin to a channel.
The interleaf continuous hinge significantly reduces the clearance gap compared to traditional continuous hinges. While most continuous hinges have a clearance gap of 12 mm, the interleaf design reduces this gap to just 3 mm. This innovative configuration also impacts the installation process, often resulting in a quicker and more efficient setup compared to conventional hinge designs.
Pin and barrel continuous hinges have a long barrel that runs the full length of the hinge with a pin inserted in the barrel. They are like traditional three to five inch door hinges but with a far longer barrel and pin, up to ten feet. Some designs of pin and barrel continuous hinges have edge protectors that wrap around the edge of the door to add greater strength and are capable of carrying additional weight. The wrap can be single or double, depending on the needs of the customer.
Similar to geared continuous hinges, pin and barrel continuous hinges are engineered to support heavier loads. Their robust construction makes them suitable for applications requiring substantial strength and durability.
Plastic hinges are constructed from various plastic materials, offering a lightweight and cost-effective substitute for metal hinges. They are particularly favored for their resistance to weather conditions, being both rust-proof and waterproof. These hinges are highly durable and are available in a range of colors to suit different applications. Like continuous hinges, plastic hinges can be found in lengths ranging from three to ten feet.
A key advantage of plastic hinges is their smooth, noiseless, and easy operation.
Slip joint lift-off continuous hinges feature a pin that connects to one leaf or wing, which then slides into a corresponding barrel on the other leaf or wing. These hinges are also known as take-apart or loose joint hinges. They simplify the process of removing a door or lid by allowing you to lift it off and separate the two parts of the hinge with ease.
Slip joint lift-off continuous hinges are particularly useful for doors or lids that need to be frequently detached. They come in configurations that can be left-handed, right-handed, or reversible, allowing flexibility in how the door or lid is positioned and used.
Slip-on continuous hinges are a distinctive type of hinge that can be installed on a door without the need for drilling. These hinges consist of two plastic channels joined by a flexible plastic connector. They are designed to be mounted by simply sliding the channels over the edges of the door and its frame.
Tight clearance continuous hinges can be either pin-and-barrel or gear type hinges that create a snug, secure seal when the door is closed. Pin-and-barrel tight clearance continuous hinges are typically made of metal and feature closely fitting knuckles. These hinges are ideal for applications where a tight seal is necessary, such as in enclosures needing protection from environmental elements or for enhanced security.
Among the various hinge types, continuous hinges are notable for their extended length, spanning the entire height of the door or lid they support. Unlike the conventional three, four, or five-inch hinges commonly found in residential, commercial, and retail settings, continuous hinges can extend from six to eight feet while maintaining a similar design to their shorter counterparts.
Typically, doors, lids, cabinets, and openings are supported by two to four smaller hinges that facilitate easy swinging movement. However, in environments where durability and strength are crucial, continuous hinges offer a more robust and resilient alternative to using multiple smaller hinges.
Continuous hinges were originally known as piano hinges, a term still used by many manufacturers today. The piano, refined over centuries, required a hinge that could effectively support the lid covering the treble bridge, strings, soundboard, and tuning pins. As the design of pianos evolved, so did the need for a hinge that could provide robust support across the full length of the lid.
After several unsuccessful attempts with less durable hinges, piano makers developed the piano hinge, which spans the entire length of the lid and is capable of bearing its weight reliably.
Continuous hinges are preferred for shed and barn doors due to their durability, strength, and ability to withstand harsh conditions and frequent use. Unlike multiple smaller hinges, continuous hinges span the entire length of the door, preventing sagging and ensuring a stable, secure operation.
Before installing a continuous hinge on a shed, gate, barn, or carriage house door, it’s crucial to consider several factors. The primary considerations are the door’s weight and width, along with the properties of the material to which the hinge will be attached. These factors ensure the hinge will perform effectively and support the door properly.
Fire door continuous hinges are typically geared continuous hinges designed to comply with fire safety regulations for hospitals, commercial properties, and hotels. These hinges are constructed to achieve a three-hour fire rating, meaning they must endure high temperatures during a standard fire test. This ensures that the hinge remains operational under intense heat, providing enough time for building occupants to evacuate safely.
Continuous hinges used in prisons and detention facilities are built to withstand heavy use and severe conditions. Prison doors can weigh as much as 900 pounds and be up to four inches thick. In some instances, these hinges are equipped with electrical components that enable remote operation, locking, and unlocking from an observation station. The door system is a critical component in correctional facilities, making the reliable performance of continuous hinges essential to the secure and efficient operation of these institutions.
While continuous hinges are lightweight, they provide the necessary stability, strength, and durability required for challenging environments. This is particularly important for marine applications where exposure to saltwater can lead to corrosion and rust in metal components. Full-length continuous hinges, which are used on hatches, doors, and cabinets, are often made from materials like stainless steel to enhance their resilience.
For marine environments, continuous hinges are often treated with a protective oxide coating or waterproofing to ensure they remain durable and resistant to harsh conditions. Additionally, plastic hinges are sometimes utilized as plastic is immune to saltwater, oil, chemicals, and solvents, offering an alternative solution for marine applications.
While using multiple small hinges to support a desk top is an option, continuous hinges provide superior strength and come in styles that enhance the desk’s appearance. Installing a continuous hinge on a desk top is straightforward, provided the appropriate type of hinge is chosen. The extensive selection of continuous hinges allows you to pick one that perfectly matches the weight of the desk top, regardless of its heaviness.
Despite the straightforward design of continuous hinges, they play a crucial role in connecting doors and enabling smooth rotation around an axis. Continuous hinges find applications in a wide range of scenarios, each requiring specific materials to meet various performance needs.
Typically, continuous hinges are made from robust and durable metals, which are often considered the best choice for strength and longevity. However, advancements in technology have introduced hybrid materials that combine many of the beneficial properties of metals, offering alternative solutions for hinge construction.
Aluminum continuous hinges are lightweight, strong, resilient, and corrosion, wear, and rust resistant. One of the reasons for choosing aluminum is its low cost, which is considerably less than stainless steel. Aluminum continuous hinges are half the weight of carbon steel and brass hinges.
Stainless steel continuous hinges are made from a variety of stainless steel series, with 300 series being the most common. Stainless steel series 790 continuous hinges are approved for fire door use by Underwriters Laboratories, Inc. The corrosion resistance of stainless steel continuous hinges makes them ideal for swimming pool buildings, sewage treatment plants, and environments with salt spray.
Steel continuous hinges are engineered for heavy-duty applications, particularly for doors that exceed 300 pounds. Plain steel is suitable for indoor environments, while galvanized steel is preferred for outdoor use due to its enhanced resistance to corrosion. Steel's inherent strength and durability make it an ideal material for continuous hinges, especially for doors subjected to frequent and intense use.
The hardness of steel is influenced by its carbon content, with higher carbon levels resulting in harder steel. For continuous hinges, selecting the appropriate hardness expands their range of applications. Additionally, the knuckle size on continuous hinges varies based on door size and steel type, with two-inch knuckles being the most common choice.
Plastic continuous hinges offer a quiet, smooth, and durable alternative to metal hinges. Unlike metal hinges with gears and pins, these hinges feature a flexible joint and are molded from a single piece of plastic. To increase their strength and durability, plastic continuous hinges may be designed with added thickness.
Different types of plastic materials determine the variations in plastic hinges, with some materials offering greater resilience. Common plastics used for these hinges include acrylic, polyvinyl chloride (PVC), polyethylene terephthalate glycol (PETG), and polyolefin. Acrylic, PVC, and PETG are known for their resistance to chemicals and corrosion, while polyolefin provides protection against oil, saltwater, solvents, and UV rays.
Carbon fiber continuous hinges are stronger than metal or plastic hinges and have exceptional strength. The leaves or wings of carbon fiber hinges are made of carbon fiber with an epoxy laminate or hybrid glass. The connecting or flex unit between the wings is Kevlar filled with urethane. The fibers of carbon fiber have exceptional tensile strength with five times the strength of steel and twice the rigidity.
Continuous hinges play a crucial role in the structural integrity of buildings, offering enhanced stability, strength, and durability for doors, enclosures, and cabinets. In environments where doors and openings experience frequent use and substantial stress, continuous hinges provide several benefits over traditional three to six-inch hinges, including superior support and a longer lifespan.
One significant advantage of continuous hinges is their ability to maintain precise alignment without sagging or shifting. Because the hinge is a single, uninterrupted piece with no gaps between knuckles, it remains firmly in place and requires considerable force to move. This feature makes continuous hinges particularly valuable in critical applications such as hospital doors and fire doors, where reliable performance is essential.
Doors fitted with the conventional three to four hinges often experience shifting, sagging, and tilting under heavy use. Over time, this can cause the door to drag and lose its smooth operation. In contrast, a door equipped with continuous hinges maintains its alignment throughout its service life, avoiding issues like shifting, tilting, or sagging. The consistent design of continuous hinges ensures long-term stability and minimizes wear and tear.
In a standard hinge setup, stress is concentrated on the knuckles and pins of each individual hinge, typically in a three or four hinge configuration. Continuous hinges, however, distribute stress evenly along the entire length of the door and frame. This design helps mitigate wear from door kickback and prevents binding by evenly dispersing the impact.
Continuous hinges for doors or cabinets are installed along the entire length of both the frame and the door or cabinet. This full-length attachment helps prevent warping or sagging, ensuring stable and consistent operation.
The full-length design of continuous hinges creates a secure, tight seal that helps prevent tampering and provides enhanced security. This feature makes continuous hinges ideal for applications where security and privacy are paramount.
Continuous hinges can be easily customized to meet specific application requirements. They can be cut to the desired length without compromising their durability or performance.
Smaller hinges often have a shorter lifespan due to their size and limited durability. In contrast, the larger dimensions and robust materials of continuous hinges offer enhanced durability, allowing them to withstand prolonged use.
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