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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]
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]
Metals are commonly used. 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 variousalloys 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 includezinc,chrome, andhot-dip galvanizing.[4][5]
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]
