A nut is a fastener that has a threaded hole in it. To secure numerous parts together, nuts are nearly typically used in conjunction with a mating bolt. The two partners are kept together by a combination of their threads’ friction (with small elastic deformation), a slight stretching of the bolt, and compression of the parts to be held together.
Lock washers, jam nuts, specialist adhesive thread-locking fluid such as Loctite, safety pins (split pins) or lockwire in conjunction with castellated nuts, nylon inserts (nyloc nut), or slightly oval-shaped threads may be used in applications where vibration or rotation may force a nut loose.
Square nuts, like bolt heads, were the first to be created and were once the most prevalent, owing to their ease of fabrication, especially by hand. The greater length of each side allows a spanner to be applied with a larger surface area and more leverage at the nut, which is rare today[when?] 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 hexagonal shape is the most frequent design nowadays, for the same reasons as the bolt head: six sides provide a good granularity of angles for a tool to approach from (excellent in tight locations), but more (and smaller) corners are subject to being rounded off. The next side of the hexagon is only one sixth of a spin away, and grip is ideal. Polygons with more than six sides, on the other hand, do not provide the required grip, and polygons with fewer than six sides take longer to rotate completely. Other customized shapes, such as wingnuts for finger adjustment and captive nuts (e.g. cage nuts) for inaccessible places, are available for specific applications.
It’s difficult to tell the difference between a bolt and a screw. Bolts are designed to enter through an unthreaded hole in a component and be fixed with the help of a nut, although such a fastener can be used without a nut to tighten into a threaded component such as a nut-plate or tapped housing, according to Machinery’s Handbook. Screws, on the other hand, are utilized in components that have their own thread or are cut with their own internal thread. This definition allows for ambiguity in the description of a fastener depending on the purpose it is used for, and the terms screw and bolt are widely used to refer to the same or different fasteners by different persons or in various nations.
Bolts are frequently utilized in bolted joints. This is a combination of the nut gripping the joint axially and the bolt shank acting as a dowel, pinning the joint against sideways shear stresses. As a result, many bolts have a plain unthreaded shank (known as the grip length), which results in a superior, stronger dowel. The existence of an unthreaded shank has been cited as a distinguishing feature of bolts vs. screws, however this is more of a byproduct of their use than a distinguishing feature.
A screw is a fastener that creates its own thread in the component being secured. When the thread is tapered (as with traditional wood screws), the use of a nut is required, or when a sheet metal screw or other thread-forming screw is used. To put the joint together, you must constantly turn a screw. During assembly, many bolts are held in place by a tool or a non-rotating bolt design, such as a carriage bolt, and only the corresponding nut is turned.