Anut is a type offastener with athreaded hole. Nuts are almost always used in conjunction with a matingbolt to fasten multiple parts together. The two partners are kept together by a combination of their threads'friction with slightelastic deformation, a slightstretching of the bolt, andcompression of the parts to be held together.
Square nuts, as well as bolt heads, were the first shape made and used to be the most common largely because they were much easier to manufacture, especially by hand. While rare today[as of?] due to the reasons stated below for the preference of hexagonal nuts, they are occasionally used in some situations when a maximum amount of torque and grip is needed for a given size: the greater length of each side allows a spanner to be applied with a larger surface area and more leverage at the nut.
The most common shape today ishexagonal, for similar reasons as the bolt head: six sides give a good granularity of angles for a tool to approach from (good in tight spots), but more (and smaller) corners would be vulnerable to being rounded off. It takes only one sixth of a rotation to obtain the next side of the hexagon and grip is optimal. However, polygons with more than six sides do not give the requisite grip and polygons with fewer than six sides require greater space to manoeuvre a spanner between engagements, or the use of a ratchet. Other specialized shapes exist for certain needs, such aswingnuts for finger adjustment and captive nuts (e.g.cage nuts) for inaccessible areas.
Nuts and bolts were originally hand-crafted together, so that each nut matched its own bolt, but they were not interchangeable. This made it virtually impossible to replace lost or damaged fixers, as they were all different.Joseph Whitworth in 1841 proposed that a standard should be set, but it did not happen immediately.
In 1851, theGreat Exhibition of the Works of Industry of All Nations was to be held in Hyde Park, London, England, and it was decided to buildthe Crystal Palace as part; this had to be done in 190 days, and at reasonable cost. Research into the remains of the destroyed building in 2024 revealed a major innovation that made this possible. The construction firm responsible, Fox Henderson, decided to use nuts and bolts, but to use standardised sizes, a revolutionary method at the time. This enabled the building to be completed in time. The use of interchangeable nuts and bolts was so successful that the Whitworth standard was widely adopted. ABritish standard was not formally adopted until 1905.[2]
There is a wide variety of nuts, fromhousehold hardware versions to specialized industry-specific designs that areengineered to meet varioustechnical standards. Fasteners used in automotive, engineering, and industrial applications usually need to be tightened to a specifictorque setting, using atorque wrench. Nuts are graded with strength ratings compatible with their respective bolts; for example, an ISO property class 10 nut will be able to support the boltproof strength load of an ISO property class 10.9 bolt without stripping.
A (usually square) nut in a spring steel cage which wraps around the nut. The cage has two wings that when compressed allow the cage to be inserted into the square holes
Used with strut to join things to the open face thereof. The grooves in its face engage the lips of the open side of the strut channel, while the spring pushes against the opposite side, to hold the nut in place.
Four-sided nut. Compared to standard hex nuts, square nuts have a greater surface in contact with the part being fastened, and therefore provide greater resistance to loosening (though also greater resistance to tightening)[4]
Many specialised types of nut exist to resist loosening ofbolted joints, either by providing a prevailingtorque against the male fastener or by gripping against the bolted components. These are generally referred to as locknuts.
Note that flat (spanner or wrench) sizes differ between industry standards. For example, wrench sizes of fastener used in Japanese built cars comply with JIS automotive standard.
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Hex nuts, recognized by their six-sided shape, andsquare nuts, with a square form, are commonly used. Steel nuts are strong and great for construction, whilestainless steel ones resist rust, perfect for outdoor use. Brass nuts,corrosion-resistant, find their place in electrical and plumbing work. Lock nuts, like nylon-insert or prevailing torque types, prevent loosening due to vibration ortorque, catering to specific needs across industries.
Mechanical specifications of Metric/English sized nuts[6]
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The manufacturing process of nuts involves several steps. It begins with the selection ofraw materials like steel, stainless steel, or brass, depending on the desired type of nut. The chosen material undergoes heating to make it moremalleable, followed by forming or forging processes to create the basic shape of the nut. Threads are then cut or formed onto the nut using specialized machinery. After threading, nuts may undergo additional treatments such asheat treatment orsurface finishing to enhance their strength, durability, or appearance. Quality control checks are performed throughout the manufacturing process to ensure that the nuts meet industry standards and specifications.
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