A fastener (US English) or fastening (UK English) is a hardware device that mechanically joins or affixes two or more objects together. In general, fasteners are used to create non-permanent

joints A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

; that is, joints that can be removed or dismantled without damaging the joining components. Steel fasteners are usually made of

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

carbon steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, cobalt ...

, or

alloy steel Alloy steel is steel that is Alloy, alloyed with a variety of elements in amounts between 1.0% and 50% by weight, typically to improve its List of materials properties#Mechanical properties, mechanical properties. Types Alloy steels divide into ...

. Other methods of joining materials, some of which may create permanent joints, include: crimping,

welding Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, primarily by using high temperature to melting, melt the parts together and allow them to cool, causing Fusion welding, fusion. Co ...

soldering Soldering (; ) is a process of joining two metal surfaces together using a filler metal called solder. The soldering process involves heating the surfaces to be joined and melting the solder, which is then allowed to cool and solidify, creatin ...

, brazing, taping, gluing,

cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...

, or the use of other adhesives.

Force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...

may also be used, such as with

magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

vacuum A vacuum (: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective (neuter ) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressur ...

(like suction cups), or even

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...

(like sticky pads). Some types of woodworking joints make use of separate internal reinforcements, such as

dowel The dowel is a cylindrical shape made of wood, plastic, or metal. In its original manufactured form, a dowel is long and called a ''dowel rod'', which are often cut into shorter ''dowel pins''. Dowels are commonly used as structural reinforceme ...

s or

biscuits A biscuit is a Flour, flour-based baked food item. Biscuits are typically hard, flat, and Unleavened bread, unleavened. They are usually sweet and may be made with sugar, chocolate, icing (food), icing, jam, ginger, or cinnamon. They can also ...

, which in a sense can be considered fasteners within the scope of the joint system, although on their own they are not general-purpose fasteners. Furniture supplied in flat-pack form often uses cam dowels locked by cam locks, also known as ''conformat fasteners''. Fasteners can also be used to close a container such as a bag, a box, or an envelope; or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container, etc. There are also special-purpose closing devices, e.g., a

bread clip A bread clip is a device that is used to hold plastic bags closed, such as those in which sliced bread is commonly packaged. They are also commonly called bread tags, bread tabs, bread ties, bread buckles, bread-bag clips, or occlupanids. By seal ...

. Items like a

rope A rope is a group of yarns, Plying, plies, fibres, or strands that are plying, twisted or braided together into a larger and stronger form. Ropes have high tensile strength and can be used for dragging and lifting. Rope is thicker and stronger ...

, string,

wire file:Sample cross-section of high tension power (pylon) line.jpg, Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample d ...

cable Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...

chain A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A ...

, or plastic wrap may be used to mechanically join objects; however, because they have additional common uses, they are not generally categorized as fasteners. Likewise,

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 ...

s and springs may join objects together, but they are ordinarily not considered fasteners because their primary purpose is to allow articulation rather than rigid affixment.

Industry

In 2005, it was estimated that the United States fastener industry runs 350 manufacturing plants and employs 40,000 workers. The industry is strongly tied to the production of automobiles, aircraft, appliances, agricultural machinery, commercial construction, and infrastructure. More than 200 billion fasteners are used per year in the U.S., 26 billion of these by the automotive industry. The largest distributor of fasteners in North America is the Fastenal Company.

Materials

There are three major steel fasteners used in industries:

, and

. The major grade used in stainless steel fasteners: 200 series, 300 series, and 400 series. Titanium, aluminium, and various alloys are also common materials of construction for metal fasteners. In many cases, special coatings or

plating Plating is a finishing process in which a metal is deposited on a surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve solderab ...

may be applied to metal fasteners to improve their performance characteristics by, for example, enhancing corrosion resistance. Common coatings/platings include zinc, chrome, and

hot-dip galvanizing Hot-dip galvanization is a form of galvanization. It is the process of coating iron and steel with zinc, which alloys with the surface of the base metal when immersing the metal in a bath of molten zinc at a temperature of around . When expos ...

Applications

When selecting a fastener for industrial applications, it is important to consider a variety of factors. The threading, the applied load on the fastener, the stiffness of the fastener, and the number of fasteners needed should all be taken into account. When choosing a fastener for a given application, it is important to know the specifics of that application to help select the proper material for the intended use. Factors that should be considered include: *Accessibility *Environment, including temperature, water exposure, and potentially corrosive elements *Installation process *Materials to be joined *Reusability *Weight restrictions

Types

A threaded fastener has internal or external

screw thread A screw thread is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a ''straight'' thread and t ...

s. The most common types are the

screw A screw is an externally helical threaded fastener capable of being tightened or released by a twisting force (torque) to the screw head, head. The most common uses of screws are to hold objects together and there are many forms for a variety ...

, nut and bolt, possibly involving

washers Washer most commonly refers to: *Washer (hardware), a thin usually disc-shaped plate with a hole in the middle typically used with a bolt or nut *Washing machine, for cleaning clothes Washer may also refer to: *Dishwasher, a machine for cleani ...

. Other more specialized types of threaded fasteners include captive threaded fasteners, stud,

threaded insert A threaded insert, also known as a threaded bushing, is a fastener element that is inserted into an object to add a threaded hole. They may be used to repair a stripped threaded hole, provide a durable threaded hole in a soft material, place a t ...

s, and threaded rods. Other types of fastener include: *

anchor bolt Anchor bolts are used to connect structural and non-structural elements to concrete.. The connection can be made by a variety of different components: anchor bolts (also named fasteners), steel plates, or stiffeners. Anchor bolts transfer diffe ...

batten A batten is most commonly a strip of solid material, historically wood but can also be of plastic, metal, or fiberglass. Battens are variously used in construction, sailing, and other fields. In the lighting industry, battens refer to linea ...

bolt (fastener) A bolt is an externally helical threaded fastener capable of being tightened or released by a twisting force ( torque) to a matching nut. The bolt has an external male thread requiring a matching nut with a pre-formed female thread. Histor ...

* bolt snap *

brass fastener A brass fastener, butterfly clips, brad, paper fastener or split pin is a stationery item used for securing multiple sheets of paper together. A patent of the fastener was issued in 1866 to George W. McGill. The fastener is inserted into punche ...

* buckle *

button A button is a fastener that joins two pieces of fabric together by slipping through a loop or by sliding through a buttonhole. In modern clothing and fashion design, buttons are commonly made of plastic but also may be made of metal, wood, or ...

* cable tie *

cam Cam or CAM may refer to: Science and technology * Cam (mechanism), a mechanical linkage which translates motion * Camshaft, a shaft with a cam * Camera or webcam, a device that records images or video In computing * Computer-aided manufacturin ...

* captive fastener * clamp (or cramp) **

hose clamp A hose clamp is a device used to attach and seal a hose (tubing), hose onto a fitting such as a barb (hose), barb or nipple (plumbing), nipple. Materials The core range of hose clamps on the open market are made from materials like stainles ...

* clasp and

shackle A shackle (or shacklebolt), also known as a gyve, is a U-shaped piece of metal secured with a clevis pin or Bolt (fastener), bolt across the opening, or a hinged metal loop secured with a quick-release locking pin mechanism. The term also appl ...

** bolt snap **

carabiner A carabiner or karabiner (), often shortened to biner or to crab, colloquially known as a (climbing) clip, is a specialized type of shackle, a metal loop with a spring-loaded gate used to quickly and reversibly connect components, most notabl ...

** circle cotter ** lobster clasp * cleco * clip ** Binder clip ** Bulldog clip ** Crocodile clip **

circlip A circlip (a portmanteau of "circle" and "clip"), also known as a C-clip, snap ring, or Jesus clip, is a type of fastener or retaining ring that consists of a semi-flexible metal ring with open ends that can be snapped into place into a Machini ...

Clothespin A clothespin (US English) or clothes peg (UK English), also spelled "clothes pin" is a fastener used to hang up clothes for drying, usually on a clothes line. Clothespins come in many different designs. Design During the 1700s laundry was ...

** hairpin clip ** paper clip ** terry clip *

clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

drawing pin A drawing pin (in British English) or thumb tack (in North American English), also called a push-pin, is a short, small pin or nail with a flat, broad head that can be pressed into place with pressure from the thumb, often used for hanging ...

(thumbtack) *

flange A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of a steel beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer o ...

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

* grommet * hook-and-eye closure * hook and loop fastener **

Velcro Velcro IP Holdings LLC, trading as Velcro Companies and commonly referred to as Velcro (pronounced ), is a British privately held company, founded by Swiss electrical engineer George de Mestral in the 1950s. It is the original manufacturer of ho ...

latch A latch or catch (called sneck in Northern England and Scotland) is a type of mechanical fastener that joins two or more objects or surfaces while allowing for their regular separation. A latch typically engages another piece of hardware on the ...

* nail and

rivet A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylinder (geometry), cylindrical shaft with a head on one end. The end opposite the head is called the ''tail''. On installation, the deformed e ...

** solid/round head rivets ** semi-tubular rivets ** blind (pop) rivet * pegs **

tent peg A tent peg (or tent stake) is a spike, usually with a hook or hole on the top end, typically made from wood, metal, plastic, or composite material, pushed or driven into the ground for holding a tent to the ground, either directly by attaching to ...

* PEM nut * pins ** clevis fastener ** cotter **

** linchpin ** R-clip **

safety pin A safety pin is a variation of the regular Pin (device), pin which includes a simple Spring (device), spring mechanism and a clasp. The clasp forms a closed loop to properly fasten the pin to whatever it is applied to and covers the end of the p ...

** split pin ** spring pin ** tapered pin * retaining rings **

** e-ring * rivet-like ** well nut * rock bolt *

rubber band A rubber band (also known as an elastic, gum band or lacky band) is a loop of rubber, usually ring or oval shaped, and commonly used to hold multiple objects together. The rubber band was patented in England on March 17, 1845, by Stephen Perry ...

(or bands of other materials) * screw anchor * snap fastener * snap-fit * staple * stitches *

strap A strap, sometimes also called strop, is an elongated flap or ribbon, usually of leather or other flexible materials. Thin straps are used as part of clothing or baggage, or bedding such as a sleeping bag. See for example spaghetti strap, s ...

* tie * toggle bolt * tolerance rings * treasury tag *

twist tie A twist tie is a fastener made of one or more metal wires encased in a thin strip of paper or plastic, in such a way that it can bend and retain its shape. Wireless polymeric twist ties have also been developed. Use It is used to tie the opening ...

* wedge anchor *

zipper A zipper (N. America), zip, zip fastener (UK), formerly known as a clasp locker, is a commonly used device for binding together two edges of textile, fabric or other flexible material. Used in clothing (e.g. jackets and jeans), luggage and oth ...

Common fastener head styles

Common head styles include: * Flat head fasteners: Ideal for applications where aesthetics are a priority, flat head fasteners sit flush with the surface, offering a clean appearance. * Round head fasteners: With a rounded top, round head fasteners provide a larger bearing surface, suitable for sheet metal or thin plastic assemblies. * Pan head fasteners: Pan head fasteners combine a slightly flattened top with a larger bearing surface, offering a streamlined appearance for aesthetic applications. * Socket head fasteners: Designed for high torque applications, socket head fasteners are driven with a hex key, reducing the risk of cam-out. * Hex head fasteners: Known for their high torque capacity, hex head fasteners are easily driven with a spanner or wrench, ideal for heavy-duty applications. * Square head fasteners: Offering increased wrenching area and reduced risk of rounding off, square head fasteners are used in high torque applications. * Flange head fasteners: Integrating a flange for a larger bearing surface, flange head fasteners distribute clamping force without damaging the material. * Wing head fasteners: Featuring protruding "wings" for hand tightening, wing head fasteners are suitable for applications requiring frequent adjustments. * T-slot fasteners: Designed for T-slotted aluminium extrusions, T-slot fasteners provide a secure and adjustable connection for framing and guarding systems.

Standards & traceability

There are multiple standards bodies for fasteners, including the US Industrial Fasteners Institute and the European Industrial Fastener Institute.

ASME B18 standards on certain fasteners

The American Society of Mechanical Engineers (

ASME The American Society of Mechanical Engineers (ASME) is an American professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing edu ...

) publishes several standards on fasteners. Some are: * B18.3 Socket Cap, Shoulder, Set Screws, and Hex Keys (Inch Series) * B18.6.1 Wood Screws (Inch Series) * B18.6.2 Slotted Head Cap Screws, Square Head Set Screws, And Slotted Headless Set Screws (Inch Series) * B18.6.3 Machine Screws, Tapping Screws, and Metallic Drive Screws (Inch Series) * B18.18 Quality Assurance For Fasteners * B18.24 Part Identifying Number (PIN) Code System Standard for B18 Fastener Products

For military hardware

American screws, bolts, and nuts were historically not fully interchangeable with their British counterparts, and therefore would not fit British equipment properly. This, in part, helped lead to the development of numerous

United States Military Standard A United States defense standard, often called a military standard, "MIL-STD", "MIL-SPEC", or (informally) "MilSpecs", is used to help achieve standardization objectives by the United States Department of Defense. Standardization is beneficial ...

s and specifications for the manufacturing of essentially any piece of equipment that is used for military or defense purposes, including fasteners. World War II was a significant factor in this change. A key component of most military standards is

traceability Traceability is the capability to trace something. In some cases, it is interpreted as the ability to verify the history, location, or application of an item by means of documented recorded identification. Other common definitions include the capa ...

. Put simply, hardware manufacturers must be able to trace their materials to their source, and provide traceability for their parts going into the

supply chain A supply chain is a complex logistics system that consists of facilities that convert raw materials into finished products and distribute them to end consumers or end customers, while supply chain management deals with the flow of goods in distri ...

, usually via bar codes or similar methods. This traceability is intended to help ensure that the right parts are used and that quality standards are met in each step of the manufacturing process; additionally, substandard parts can traced back to their source.

History

In 1988, the

United States House Energy Subcommittee on Oversight and Investigations The U.S. House Energy Subcommittee on Oversight and Investigations is a subcommittee within the House Committee on Energy and Commerce. Jurisdiction Responsibility for oversight of agencies, departments, and programs within the jurisdiction of th ...

investigated counterfeit, mismarked, substandard fasteners and found extensive use in critical civilian and military infrastructure. As a result, they proposed ''Fastener Quality Assurance Act of 1988'' (HR5051) that would require laboratory testing of fasteners in critical use applications prior to sale.