Mechanical bearing connecting two objects
An ornate brass door hinge
A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation, with all other translations or rotations prevented; thus a hinge has one degree of freedom. Hinges may be made of flexible material or moving components. In biology, many joints function as hinges, such as the elbow joint.
Ancient remains of stone, marble, wood, and bronze hinges have been found. Some date back to at least Ancient Egypt.
In Ancient Rome, hinges were called cardō and gave name to the goddess Cardea and the main street Cardo. This name cardō lives on figuratively today as "the chief thing (on which something turns or depends)" in words such as cardinal.
According to the OED, the English word hinge is related to hang.
- Barrel hinge
- A barrel hinge consists of a sectional barrel (the knuckle) secured by a pivot. A barrel is simply a hollow cylinder. The vast majority of hinges operate on the barrel principle.
- Butt hinge / Mortise hinge
- Any hinge designed to be set into a door frame and/or door is considered a butt hinge or mortise hinge. A hinge can also be made as a half-mortise, where only one half us mortised and the other is not. Most mortise hinges are also barrel hinges because of how they pivot (i.e., a pair of leaves secured to each other by knuckles through which runs a pin).
- Butterfly / Parliament (UK) hinge
- A decorative variety of barrel hinge with leaves somewhat resembling the wings of a butterfly
- Case hinge
- Similar to butt hinges, but usually more decorative; most commonly used in suitcases, briefcases, and the like
- Concealed hinge
- Used for furniture doors (with or without a self-closing features and/or damping systems),they consist of two parts: (1.) the cup and arm, and (2.) the mounting plate. They are also called "cup hinges", or "Euro hinges", as they were developed in Europe and use metric installation standards. Most concealed hinges offer the advantage of full in situ adjustability for standoff distance from the cabinet face, as well as pitch and roll by means of two screws on each hinge.
- Continuous / Piano hinge
- This variety of barrel hinge runs the entire length of a door, panel, box, etc. They are manufactured with or without holes.
- Flag hinge
- A simple two-part hinge, where a single leaf, attached to a pin, is inserted into a leaf with a hole. This allows the hinged objects to be easily removed (such as removable doors). They are made in right- and left-hand configurations.
- H hinge
- These H-shaped barrel hinges are used on flush-mounted doors. Small H hinges (3–4 in or 76–102 mm) tend to be used for cabinets, while larger ones (6–7 in or 150–180 mm) are for passage doors and closet doors.
- HL hinge
- Commonly used for passage doors, room doors, and closet doors in the 17th, 18th, and even 19th centuries. On taller doors, H hinges were occasionally used between them.
- Pivot hinge
- This hinge pivots in openings in the floor and the top of the door frame. Also referred to as double-acting floor hinges, they are found in ancient dry stone buildings and, rarely, in old wooden buildings. They are a low-cost alternative for use with lightweight doors. Doors with these hinges may be called haar-hung doors.
- Self-closing hinge
- This is a spring-loaded hinge with a speed control function. The same as spring hinge, usually use spring to provide force to close the door and provide a mechanical or hydraulic damper to control door close speed. That can prevent door slamming problem while auto closes a door.
- Spring hinge
- A spring-loaded hinge that provides assistance in closing or opening the hinge leaves. An inner spring applies force to keep the hinge closed or opened.
- Swing Clear hinge
- Also called offset door hinges, they are ideal for residential and commercial doors, they allow doors to swing completely clear of their openings. They can easily comply with Fair Housing Act (FHA) code by providing a minimum ADA 32” clearance when using a 34” door slab.
- Living hinge
- A hinge of flexible plastic that creates a join between two objects without any knuckles or pins. Molded as a single piece, they never trust or squeak, and have several other advantages over other hinges, but are more susceptible to breakage.
Other types of hinges include:
- Cranked or storm-proof
- Double action non-spring
- Double action spring
- Pinge (with a quick-release pin)
- Rising butt
Since at least medieval times, there have been hinges to draw bridges for defensive purposes for fortified buildings. Hinges are used in contemporary architecture where building settlement can be expected over the life of the building. For example, the Dakin Building in Brisbane, California, was designed with its entrance ramp on a large hinge to allow settlement of the building built on piles over bay mud. This device was effective until October 2006, when it was replaced due to damage and excessive ramp slope.
Hinges appear in large structures such as elevated freeway and railroad viaducts, to reduce or eliminate the transfer of bending stresses between structural components, typically in an effort to reduce sensitivity to earthquakes. The primary reason for using a hinge, rather than a simpler device such as a slide, is to prevent the separation of adjacent components. When no bending stresses are transmitted across the hinge, it is called a zero moment hinge.
A variety of self-actuating, self-locking hinges have been developed for spacecraft deployable structures such as solar array panels, synthetic aperture radar antennas, booms, radiators, etc.