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; that is, joints that can be removed or dismantled without damaging the joining components.
Other methods of joining materials, some of which may create permanent joints, include: crimping, welding, soldering, brazing, taping, gluing, cement, stitching, sewing, press-fitting, shrink-fitting or the use of other adhesives. Force may also be used, such as with magnets, vacuum (like suction cups), or even friction (like sticky pads). Some types of woodworking joints make use of separate internal reinforcements, such as dowels or biscuits, 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.
Items like a rope, string, wire, cable, chain, 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, hinges 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.
Metals are commonly used. There are three major steel fasteners used in industries: stainless steel, carbon steel, and alloy 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 or plating 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.
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:
Types
A threaded fastener has internal or external screw threads. The most common types are the screw, nut and bolt, possibly involving washers.
Other more specialized types of threaded fasteners include captive threaded fasteners, stud, threaded inserts, and threaded rods.
Other types of fastener include:
Common head styles include:
There are multiple standards bodies for fasteners, including the US Industrial Fasteners Institute and the European Industrial Fastener Institute.
The American Society of Mechanical Engineers (ASME) publishes several standards on fasteners. Some are:
Reference: Wikipedia
