Bolts are fasteners that hold together two or more pieces of metal. They are a form of threaded fasteners consisting of a male external thread. Bolts and screws are generally mistaken to be identical, but both have several application differences. Bolts are used to assemble two unthreaded components along with a nut.
They come in various sizes and can be made from different materials, depending on their intended use. Bolts are typically inserted into pre-drilled holes and secured with a nut, although some bolts can be self-locking. Earlier bolts with square head shapes were popular and were formed through forging. Nowadays, hexagonal-headed bolts have become highly popular. Spanners and wrenches of various forms are used to tighten these bolts. Some bolts even come with T-heads and Slotted heads. Bolts come with multiple head types like Anchor, Carriage, Elevator, Hanger, Arbour, Hex, J-Bolt, Rock, Lag Bolt, U-Bolt, Eye bolt, and more. Carriage bolts have a smooth, rounded head and square or flat neck that prevents the bolt from turning when tightened. Eye bolts have a circular ring on the end of the shank and are used to secure cable and rope. Hex bolts have six-sided heads and are used in heavy machinery. Lag bolts have large, blunt heads and are used to secure the wood. Various materials are used in forging bolts, applicable in different situations. Stainless steel bolts are used for their strength, Bronze and Brass Bolts are used for their water-resistant properties, and Nylon Bolts are used for lightweight and water-resistance. Stainless Steel is the most commonly used material for Bolts.
Bolts are one of the most widely used fasteners for various applications. From complex structures like bridges and building frameworks to more everyday items such as furniture, bicycle parts, and car engines - bolts can be found at work in almost any industry. For example, turrets used in water tanks must be joined with nuts and bolts with enough tensile strength to withstand the pressure from above. When it comes to ensuring that electrical components are securely held together, threaded studs or bolts offer an extremely reliable connection due to their greater physical strength than other fasteners. Bolts also come into play when securing doors or gates, providing a secure framework for deadbolts or padlocks to latch onto. The fact that they are so versatile makes bolts an indispensable element in construction and maintenance projects across all fields
Hex bolts are one of the most commonly used types of bolts.
The strength of a bolt depends on its material, size, and design. However, high-strength bolts such as structural bolts (ASTM A325 and A490) are among the strongest.
The choice of metal for bolts depends on the specific application and requirements. Some commonly used metals for bolts include steel, stainless steel, titanium, and brass. Each metal has unique properties that make it suitable for different applications. For example, steel is solid and durable, while stainless steel offers corrosion resistance.
Bolts should be replaced if they show signs of wear, damage, or corrosion that could compromise their strength and performance. It is also recommended to replace bolts if they have been subjected to excessive stress or loading. Additionally, bolts should be replaced if they are part of a safety-critical system or application, and the manufacturer recommends periodic replacement as part of maintenance procedures. Regular inspections can help identify bolts that need to be replaced before they fail.
There are several bolt-tightening methods, including:
The choice of tightening method depends on factors such as the type of application, the size and strength of the bolts, and the desired level of precision in achieving proper bolt preload.
Stainless steel bolts are known for their resistance to rust and corrosion due to the high amounts of chromium in the material. This makes them a popular choice for outdoor and marine applications and in harsh environments where exposure to moisture or chemicals is common. Other types of non-rusting bolts include those made from titanium, aluminium, and brass, which are also valued for their durability and resistance to corrosion.
Hex bolts are one of the most commonly used types of bolts.
Bolts are typically measured by their diameter, length, and thread pitch. The diameter of a bolt is measured across the shank, or body, of the bolt. The length of a bolt is measured from under the head to the end of the shank. Thread pitch refers to the distance between adjacent threads on a bolt and is typically measured in threads per inch (TPI) or millimetres.
A T-slot bolt is designed to fit into a rectangular slot, also known as a T-slot, commonly found in machine tool tables and workbenches. These bolts have a flat, T-shaped head that fits snugly into the slot and can be tightened or loosened with a hex key or wrench.
The amount of bolt that should stick out depends on the specific application and the type of bolt being used. Generally, bolts should protrude at least one thread pitch beyond the nut to ensure proper engagement and prevent loosening. However, in some cases, a more extended protrusion may be required to add strength or accommodate additional hardware.
Bolts are typically made through cold forging, in which a metal wire is fed into a machine and then cut to length. The wire is then heated and shaped using dies to create the desired bolt shape, including the head, shank, and threads. After forming, the bolts are often treated with heat or surface coatings to improve their strength or corrosion resistance.
The most common grading system for bolts is the SAE (Society of Automotive Engineers) system, which assigns grades based on the bolt's tensile strength, yield strength, and hardness. Higher-grade bolts are more robust and can withstand heavier loads and extreme conditions. Some other grading systems used for bolts include ASTM (American Society for Testing and Materials) and ISO (International Organization for Standardization).
Bolts are used in various applications, from simple household repairs to complex machinery and infrastructure projects. They are commonly used in construction, manufacturing, automotive, aerospace, and many other industries where solid and reliable fasteners are needed. Bolts can be found in everything from bridges and buildings to cars and aeroplanes, as well as in everyday items like furniture and electronics.
Bolt pre-load is the tension force that is applied to a bolt when it is tightened. This force creates an elastic deformation in the bolt and the parts being fastened together, which helps hold them securely. The amount of pre-load required for a given application depends on factors such as the size and strength of the bolts, the material properties of the parts being fastened together, and the expected loading conditions.
Properly achieving and maintaining bolt pre-load is essential for ensuring joints remain tight and secure over time. Insufficient pre-load can result in joint failure due to movement or vibration, while excessive pre-load can lead to bolt fatigue or fracture. Bolt tightening methods such as torque, angle, yield, and tensioning are used to achieve proper bolt pre-load based on specific application requirements.
The type of bolt without a head is called a "stud". A stud has threads on both ends and is designed to be installed into a tapped hole on one end, with a nut threaded onto the other end to secure the parts being fastened together. Since it does not have a head, studs are often used in applications with limited clearance or where frequent assembly and disassembly may be required.