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Afastener (US English) orfastening (UK English)[1] is ahardware device that mechanically joins or affixes two or more objects together. In general, fasteners are used to create non-permanentjoints; that is, joints that can be removed or dismantled without damaging the joining components.[2] Steel fasteners are usually made ofstainless steel,carbon steel, oralloy steel.
Other methods of joining materials, some of which may create permanent joints, include:crimping,welding,soldering,brazing,taping,gluing,cement, or the use of other adhesives.Force may also be used, such as withmagnets,vacuum (likesuction cups), or evenfriction (likesticky pads). Some types ofwoodworking joints make use of separate internal reinforcements, such asdowels orbiscuits, 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 inflat-pack form often usescam dowels locked bycam locks, also known asconformat 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 alid to a container, etc. There are also special-purpose closing devices, e.g., abread clip.
Items like arope, string,wire,cable,chain, orplastic wrap may be used to mechanically join objects; however, because they have additional common uses, they are not generally categorized as fasteners. Likewise,hinges andsprings may join objects together, but they are ordinarily not considered fasteners because their primary purpose is to allow articulation rather than rigid affixment.
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 theFastenal Company.[3]
There are three major steel fasteners used in industries:stainless steel,carbon steel, andalloy steel. 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 orplating may be applied to metal fasteners to improve their performance characteristics by, for example, enhancing corrosion resistance. Common coatings/platings include zinc, chrome, andhot-dip galvanizing.[4][5]
1. Stainless Steel Fasteners
Stainless steel fasteners are made from chromium-containing alloys available in 200, 300, and 400 series. They offer strong corrosion resistance, good strength, and suitability for chemical, marine, and outdoor applications. Stainless steel fasteners remain structurally stable under heat and moisture.
2. Carbon Steel Fasteners
Carbon steel fasteners use steel with controlled carbon content, providing strength, hardness, and cost-effectiveness. They are widely used in construction, machinery, and automotive applications. Carbon steel fasteners often require protective coatings to resist corrosion.
3. Alloy Steel Fasteners
Alloy steel fasteners are produced by adding chromium, molybdenum, nickel, and other alloying elements to enhance hardness and toughness. They perform well under high stress and high temperature. Alloy steel fasteners are common in heavy engineering, oil & gas, and power generation.
4. Titanium Fasteners
Titanium fasteners are lightweight, extremely strong, and highly corrosion resistant, even in seawater and aggressive chemicals. They offer an excellent strength-to-weight ratio.Titanium fasteners are widely used in aerospace, marine, and chemical industries.
5. Aluminium Fasteners
Aluminium fasteners are lightweight and corrosion resistant, suitable for applications requiring reduced weight. They offer moderate strength and good electrical/thermal conductivity. Aluminium fasteners are common in automotive, electronics, and light structural use.
6. Brass Fasteners
Brass fasteners are made from copper-zinc alloys that provide excellent corrosion resistance and electrical conductivity. They are easy to machine and resistant to tarnish. Brass fasteners are used in plumbing, electrical fittings, and decorative applications.
7. Copper Fasteners
Copper fasteners offer high electrical and thermal conductivity along with good corrosion resistance. They are commonly used in electrical equipment and environments requiring non-magnetic properties. Copper fasteners also resist biofouling in marine applications.
8. Bronze Fasteners
Bronze fasteners, made from copper-tin alloys, provide high strength and superior corrosion resistance in saltwater. They perform reliably in marine and industrial environments. Bronze fasteners are valued for durability and low friction properties.
9. Nickel Alloy Fasteners
Nickel alloy fasteners (e.g., Inconel, Monel, Hastelloy) are engineered for extreme environments involving high temperature, pressure, and corrosion. They maintain strength and stability in acidic, alkaline, and high-heat applications. Nickel alloy fasteners are widely used in aerospace and chemical processing.
10. Copper-Nickel Fasteners (Cu-Ni)
Copper-nickel fasteners provide excellent resistance to seawater corrosion and biofouling. They maintain stability in high-salinity conditions. Copper-nickel fasteners are used in shipbuilding, desalination plants, and marine engineering.
11. Plastic / Polymer Fasteners
Plastic fasteners are made from nylon, PVC, polypropylene, or PTFE and provide corrosion-free and lightweight solutions. They are electrically insulating and resistant to many chemicals. Plastic fasteners are used in electronics, consumer products, and non-load-bearing applications.
12. Composite Fasteners
Composite fasteners use fiber-reinforced materials such as fiberglass or carbon fiber for high strength and non-metallic performance. They offer corrosion resistance and electrical insulation. Composite fasteners are used in aerospace, defense, and advanced engineering.
13. Zinc-Coated Fasteners
Zinc-coated fasteners use a thin zinc layer to protect steel through sacrificial corrosion resistance. They are economical and suitable for general outdoor use. Zinc-coated fasteners offer moderate corrosion protection for construction and hardware applications.
14. Chrome-Plated Fasteners
Chrome-plated fasteners have a chromium coating that enhances wear resistance, corrosion resistance, and surface hardness. They also provide a polished, decorative finish. Chrome-plated fasteners are used in automotive, hardware, and aesthetic applications.
15. Hot-Dip Galvanized Fasteners
Hot-dip galvanized fasteners are steel fasteners coated in molten zinc, forming a thick, durable protective layer. They provide long-term rust protection in harsh and outdoor environments. Hot-dip galvanized fasteners are used in infrastructure, marine, and structural applications.
16. Tantalum Fasteners
Tantalum fasteners are highly resistant to strong acids such as hydrochloric and sulfuric acid. They remain stable in extreme corrosion conditions and high temperatures. Tantalum fasteners are used in chemical reactors and medical equipment.
17. Zirconium Fasteners
Zirconium fasteners offer exceptional corrosion resistance in acidic and alkaline environments, including high-temperature chemical processes. They are also non-magnetic and heat resistant. Zirconium fasteners are used in nuclear, chemical, and pharmaceutical industries.
18. Superalloy (High-Performance Alloy) Fasteners
Superalloy fasteners are made from high-temperature alloys designed to maintain strength and corrosion resistance during extreme conditions. They perform well under heavy mechanical stress. Superalloy fasteners are used in turbines, jet engines, and aerospace systems.
When selecting a fastener for industrial applications, it is important to consider a variety of factors. The threading, the appliedload 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:
Athreaded fastener has internal or externalscrew threads.[7] The most common types are thescrew,nut andbolt, possibly involvingwashers.
Other more specialized types of threaded fasteners includecaptive threaded fasteners,stud,threaded inserts, andthreaded rods.
Other types of fastener include:
Common head styles include:[8]
There are multiplestandards bodies for fasteners, including the USIndustrial Fasteners Institute and theEuropean Industrial Fastener Institute.
The American Society of Mechanical Engineers (ASME) publishes several standards on fasteners. Some are:
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 numerousUnited States Military Standards 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 istraceability. Put simply, hardware manufacturers must be able to trace their materials to their source, and provide traceability for their parts going into thesupply chain, 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.[9]
In 1988, theUnited States House Energy Subcommittee on Oversight and Investigations investigated counterfeit, mismarked, substandard fasteners and found extensive use in critical civilian and military infrastructure.[10][11][12] As a result, they proposedFastener Quality Assurance Act of 1988 (HR5051) that would require laboratory testing of fasteners in critical use applications prior to sale.[10]
