Hinges And Pivots: The Things That Swings Doors

As locksmiths, the services we provide are normally focused on locks, lock related hardware and keys. We specify the necessary products, we will key and customize, and then install.

Locksmiths are beginning to become more aware of the door in respect to adjusting closers and replacing hinges with continuous hinges if the door sags/drags. However, there is much more that we need to consider we go out to a job. We need to be aware of the composition of the door, if the opening we will be working on is rated, as well as making sure the existing lock hardware meets standards. We must know what can and cannot be installed depending upon the location and if the opening is rated.
For this overview article, we will focus on butt hinges, pivots and continuous hinges, covering their composition and electrification for fire rated and non-fire rated openings.

BUTT HINGES
A standard three-foot wide by seven-foot tall, 1-3/4-inch thick door will usually have three butt hinges. A seven-foot door is 84 inches tall. A general rule is one butt hinge for every 30 inches for up to a 36-inch wide conventional door. Butt hinges are rated for traffic, door weight and width. Butt hinges are available in a variety of configurations.
The basic parts of a butt hinge are the two leaves and the pin. One leaf is attached to the frame. The other leaf is attached to the door and permits it to swing. The rounded portions of the butt hinge that interconnect using the pin are the barrels. Each rounded portion of the barrel is a knuckle. Standard butt hinges have either three or five knuckles. The knuckles of the two leaves are offset from each other and mesh together. A hinge pin is inserted into the two sets of knuckles to combine the leaves, making the hinge a single swinging unit. Depending upon the butt hinge, there can be decorative tips (acorn, ball, steeple), ball bearings and a removable or non-removable pin (NRP). A removable pin permits the hinge to be disassembled.
Butt hinges can be manufactured of different base materials having a variety of finishes. The base material is the metal used to construction the hinge but it may have a different finish. Butt hinges can be manufactured of aluminum, brass, bronze, steel, stainless steel, etc. A steel hinge is susceptible to corrosion and basically designed for interior applications. For exterior or hazardous applications, brass or stainless steel butt hinges are usually recommended.
For fire rated or labeled opening applications, only butt hinges manufactured of and to the standard hinge weight as specified in ANSI 156.1 and NFPA 80 meet the requirements. All of the butt hinges installed onto the fire rated openings, over 20 minutes, must be steel or stainless steel.
In 1991, the National Fire Protection Association (NFPA) released their revised NFPA 80, Standard for Doors, Windows and Other Opening Protectives (the 2007 edition has been re-named “Standard for Doors, Frames and Other Opening Protectives”), requiring annual fire door inspections.
The 1991 Edition, for the first time, called out not only what could be done to doors and frames (such as prepping them), but also made it clear that if something was not explicitly allowed, it was disallowed. Final decisions are still in the jurisdiction of the local Authority Having Jurisdiction (AHJ).
There are very specific allowances for the size, diameter and location of holes that can be placed into doors (such as the maximum of one-inch diameter). Since there was no mention of modifying a fire labeled opening or a hinge, pivot, etc., in the NFPA 80, these procedures are not allowed. Some doors and frames for fire listed and rated openings come factory prepared for electrified hinges and lock hardware. Most of the newer frames come with holes in the hinge back plate already stamped out for a center wire hinge position.
When discussing hinges, only power transfer butt hinges bearing the UL Mark (“F” in a circle) stamped into one leaf, or the recognized mark of a Nationally Recognized Testing and Listing Agency acceptable to the AHJ, should be considered to be listed for fire door applications.
The leaves of a butt hinge can be mounted into the edge of the door or frame or onto the face of the door or frame. Depending upon the mounting configuration, the butt hinge is either a full mortise, half mortise, full surface or half surface. A full mortise butt hinge has both leaves mortised into the edge of the door and the frame. A half mortise butt hinge has the door leaf mortised into the door edge and the frame leaf surface mounted onto the face of the frame. A half surface butt hinge has the door leaf surface mounted onto the door face and the frame leaf mortised into the frame. A full surface butt hinge has both leaves surface mounted onto the face of the door and the frame.
Butt hinges have been modified to provide power transfer to the locking mechanism. Early power transfer hinges were equipped with minimal gauge wires to accommodate the required minimal openings. In the 1990s, the first high amperage power transfer hinge was introduced. This hinge had two 20 gauge wires for inrush power and four smaller 30 gauge wires for controls and switches.
Important: Power transfer hinges should be installed in the center hinge location.
Power transfer hinges are designed for low voltage, 48 volts maximum. The amperage rating of the twenty gauge wires is 16 Amps inrush for 200 milliseconds and up to 3.5 Amps continuous operation. This is sufficient to operate a large solenoid powered exit device latch retraction mechanism.
What made the first high amperage power transfer hinge unique was the use of Plenum rated Teflon jacketed silver plated, stranded copper wires. The Teflon coating is significantly thinner than standard insulation enabling the use of larger gauge wires (thicker). Teflon jacketed wiring is non-flammable, suitable for harsh environments.

PIVOT HINGES
Pivot hinges (pivots) are installed along the heel edge (hinge side) of the door in openings in or on the floor and at the top of the frame. Pivots permit the door to pivot (rotate). Unlike butt hinges, pivots support the door from the floor, not the frame. A pivot set includes both the top and bottom pivots. A pivot set can support very heavy doors.
There are two types of pivots, offset and center hung. A center hung pivot supports the weight of the door from directly beneath. A door supported by a center hung pivot set can be double acting. Center hung pivot sets can provide full concealment by mounting them within the body of the door.
Offset pivots have the door offset from the center of the pivot. Offset pivots are available with the pivot point located ¾” from the heel edge and either ¾” or 1-1/2” from the face of the door. Most offset pivots are handed. For offset pivot applications, there are intermediate pivots to assist with the pivoting of heavy doors.
Pivots are available in different sizes and configurations to accommodate the varying door widths, heights, thickness and traffic flow.
For fire rated openings, the intermediate offset pivot is available for power transfer. Most intermediate electric power transfer pivots have a 20- minute label. The Marray Intermediate offset pivot, part number PVT, is manufactured from stainless steel, is UL 10C Listed and rated for three hours. Bottom offset pivots are available having up to a three hour label. If the pivot is manufactured of brass or similar material, the fire rating maximum is 20 minutes. Pivots manufactured of steel and stainless steel can have a fire rating of up to three hours.
For fire rated or labeled opening applications, only power transfer pivots bearing the UL Mark, or other recognized listing agency mark, should be considered listed for fire rated door applications. All of the pivots installed onto the Fire Listed assembly must meet the minimum fire rating requirement. Pivots must be installed according to the manufacturer’s installation instructions in order to maintain their listing status.

CONTINUOUS HINGE
The continuous hinge takes the attributes of the butt hinge and expands the leafs to the full height of the door/frame. The continuous hinge distributes the door’s weight along the entire length of the frame.
Continuous hinges are available as geared or pin and barrel. The pin and barrel continuous hinge leafs are a longer style of the butt hinges, also known as piano hinges. The geared continuous hinge leafs have geared ends in place of the knuckles. In place of the pin, the geared ends are held in place and able to swing since they are connected to the gear cap.
As the geared hinge opens and closes, the gear teeth engage and disengage, keeping the two leafs connected. The design keeps each leaf in alignment, minimizes lateral wear because the door swings evenly along the entire height.
Continuous hinges are available in aluminum, steel and stainless steel in a variety of finishes. They are available as Full Mortise, Half Mortise, Half Surface and Full Surface. Some continuous hinges are reversible. Depending upon the manufacturer, continuous hinges are available to accommodate a four-foot by ten-foot door that weighs in excess of 500 pounds.
Continuous hinges are available for fire rated openings. For most continuous hinges, there are basically two fire ratings, 1-1/2 hour (90 minutes) and 3 hours. Depending upon the manufacturer, fire pins may be required for the continuous hinge to maintain the fire rating. Most Select Product continuous hinges can be UL rated for up to 3 hour, without fire pins, using a patented process that incorporates intumescent material in specific areas of the hinge. Intumescent material swells as a result of heat exposure filling the void. This poor conductor of heat protects the surrounding materials.
Continuous hinges must be factory prepped for electrical transfer and monitoring. The electrical prep options include concealed thru wires, electrical power transfer cutout, removable panel and access panel. For monitoring applications, the prep options include concealed magnetic switch and exposed monitor switch.
The location of the UL Mark in fire rated continuous hinges can vary by manufacturer and the hinge model. Full and half surface hinges can have the UL Mark located beneath the door cover.
Continuous hinges must be installed according to the manufacturer’s installation instructions in order to maintain the UL rating. To install the hinge, all of the provided fasteners must be used in their respected locations. Failure to do so will void the UL rating. Alterations to the hinges in the field, other than cutting the hinge to a required length if necessary will void the UL rating.
Note: If the door does not properly fit the opening, continuous shim stock up to 1/8” maximum thickness, can be installed on the frame side beneath the hinge.
Continuous hinges are available in many configurations, some for specialized applications and configurations including a full wrap edge guard that protects the door edge.
There is a great deal more information regarding hinges and pivots. Contact the manufacturers engineering or technical services departments.
The following is a partial list of butt hinges, continuous hinges and pivot manufacturers and modifiers:
Hinges/Pivots: