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Bolt (fastener) and bolt head

Views: 0     Author: Site Editor     Publish Time: 2023-05-19      Origin: Site

A bolt is a threaded fastener with an external thread that requires a matching prefabricated internal thread, such as a nut.Bolts are closely related to screws.


Bolts are one of the most versatile and widely used fasteners in a variety of applications.Bolts can be found in nearly every industry, from construction items like bridges, buildings, and framing to everyday items like furniture, bicycles, and car engines.Due to their higher physical strength compared to other fasteners, studs or bolts provide an extremely reliable connection to electrical components.Bolts are also necessary to secure a door or gate providing an effective framework for a deadbolt or padlock.Such a wide range of uses of bolts makes them invaluable in construction and maintenance projects in various fields.

Bolts vs. screwsbolt head

The distinction between bolts and screws is not clear.According to the Handbook of Mechanics the academic difference is their intended design: the bolt is designed to pass through an unthreaded hole in the assembly and be secured with the aid of a nut, although such fasteners can be used without a nut into threaded parts such as a nut plate or threaded housing.In contrast, screws are used for components that contain their own threads, or have their own internal threads cut into them.This definition allows for ambiguity in describing fasteners depending on their actual use, and the terms screw and bolt are widely used by different people or in different countries to apply to the same or different fasteners.

Bolts are commonly used to make bolted connections.This is a combination of a nut that applies axial clamping force and a bolt shank that acts as a dowel and secures the joint against transverse shear forces.For this reason, many bolts have a common unthreaded shank (called the clamping length), as this makes the pin better and stronger.The presence of an unthreaded shank is generally considered to be a characteristic of bolts and screws,but this is incidental to its use rather than defining.If a fastener forms its own thread in the part being fastened, it is called a screw.This is most noticeable when the threads are tapered (i.e. traditional wood screws), so nuts cannot be used,or when using sheet metal screws or other self-tapping screws.The screws must always be turned to assemble the joint. Many bolts are held in place during assembly by tools or non-rotating bolt designs such as carriage bolts, and only the corresponding nut is turned.

Bolt head

Bolts use a variety of head designs, as do screws.These are designed to engage with the tools used to tighten them.Some bolt heads instead lock the bolt in place so it doesn't move and only requires a tool to tighten the nut end.Common bolt heads include hex, slotted hex washers, and socket caps.The first bolt has a square head and is formed by forging.These are still found, although hexagonal heads are more common today.They are held and turned by wrenches or sockets which come in many forms. Most are secured from the side, some from in-line with the bolt.Other bolts have T-heads and slotted heads. 

Many bolts use a screwdriver bit attachment rather than an external wrench.Use the screwdriver in line with the fastener, not from the side.They are smaller than most wrench heads and usually cannot apply the same amount of torque.It is sometimes assumed that a screwdriver bit means a screw and a wrench means a bolt, but this is not the case.Coach screws are large lag screws with tapered wood threads used to secure ironwork to wood.Head designs that overlap bolts and screws are Allen or Torx heads; hexagonal or splined sockets.These modern designs come in a variety of sizes and can carry considerable torque.Threaded fasteners with screwdriver-style heads are often referred to as machine screws, whether or not they are used with nuts.

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