Bolt Fasteners

Bolt Fasteners

The Background of Bolts

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Over 200 BCE, Archimedes invented a large bolt or screw pump, making use of the screw principle. The pump contained a screw with helical threads sculptured on a shaft, fitted inside a tube. It changed radically the irrigation, allowing water to be raised from low-lying water bodies. While Archimedes is renowned with this invention, historical evidence suggests that he actually borrowed the idea from the Egyptians, who he saw using wooden screw pumps for irrigation.


Modern bolts came into existence much later, in the 15th century. This occurred when a German publisher, named Johann Gutenberg, used bolts to fasten his printing presses.  With the never-ending need for screws or bolts, engineers of the time also used bolt-cutting machines.
In spite of the use of bolt-cutting machines, bolts were still made and used on a small scale until the occurrence of the Industrial Revolution. Once the Industrial Revolution happened, industrial bolts became a vital component in the engineering world.
During the 18th century, engineers designed the “first thread cutting machines”, clearing and paving the way for the mass production of screws. The reasons are different companies had their own standards for manufacturing industrial bolt threads, the market was flooded with an arrangement of different sized screw threads.
To overcome this problem, in 1841, Joseph Whitworth, an English engineer, came up with the idea of standardizing the size of the screw threads in industrial bolts. His recommendation was a standardized angle of the thread flanks and numbers of threads per inch. His efforts brought a change in the industrial bolts industry in Britain. Concurrently, across the Atlantic Ocean, American and Canadian engineers made similar efforts, making bolt threads standardized for specific diameters.\

Learn more about Nut Fasteners


World War II forced Americans, British, and Canadian manufacturing companies to assign their bolt standards so that they could support one another with vehicles and weapons. They agreed on a standard in which all countries used imperial measurements. The unified standard stated that the flank angle should be 60 degrees, the crests should be flat, and the bolts would have rounded root, which improved fatigue performance.

What is Bolt Fasteners?

Predominantly, No industry can survive in Today’s world without fasteners like screws, bolts, and nuts. The hardware parts form as essentially required by any machines, whether simple household items to complex high-end machines in industries.
Bolt is used with a nut for adjoining two or more parts. A bolted joint can be readily disassembled and reassembled; hence, bolts or screw fasteners are used to a greater extent than any other type of mechanical fastener. Having played an important part in the development of mass-produced articles and steel structures.
The bolt consists of a head and a cylindrical body with screw threads along a portion of its length. Washers are often used to prevent loosening and crushing.


In construction, fasteners are connectors between structural members.  Threaded metal bolts are always used in conjunction with nuts. Another threaded fastener is the screw, which has countless applications, especially for wood construction. The wood screw carves a mating thread in the wood, ensuring a tight fit.  Riveted connections, which resist shearing forces, were in wide use for steel construction before being replaced by welding. The rivet, visibly prominent on older steel bridges, is a metal pin fastener with one end flattened into a head by hammering it through a metal gusset plate. The common nail, less resistant to shear or pull-out forces, is useful for cabinet and finishing work, where stresses are minimal.
Screws are usually turned into an object, like a piece of wood, so the head needs to be bigger than the surface. The main distinguishing factor between a bolt and a screw is that a typical screw can work on its own and a bolt requires a nut to secure it.

A ratchet is a basic wrench device with a fastener part. A ratchet wrench is an essential tool that is used to fasten or loosen nuts and bolts.

A Gallery of 12 Common Bolt Types. Bolts are threaded fasteners that are intended to be mated with a nut.

What are Bolts?

Bolts are screws that rotate into a matched nut to tighten it. Bolts have a huge head than the shaft, including a few exceptions. Carriage bolts and J-bolts are among those exceptions. The main distinguishing feature between a bolt and a screw is that a typical screw can work on its own and a bolt requires a nut to secure it.
While People often get confused, bolts and screws are altogether different types of fasteners. Bolts are headed fasteners with external threads suitable for non-tapered nut. The bolts are made with standardized threads satisfying the standard specifications such as UNJ, UNR, MJ, etc. and are used in most industrial applications – secured with a spring-washer or a locktite.

Bolts are for the assembly of two unthreaded components, with the aid of a nut.


Most of the people know that without fasteners like screws, bolts, and nuts, no industry can survive. It is many times essential to use high-quality nuts, bolts, and screws. From small furniture crafting to oil sector industries the most essential hardware items include these fasteners – bolted joint is the most trustworthy part connection – moreover, it usually gives an option of dismantling and reinstalling.
They require a nut (or some other thread) as a counter – to lock the joint. The bolts are made with uniform threads satisfying the standard specifications such as UNJ, UNR, MJ, etc. To sum it up, bolts are designed to use as a fastener placed through already drilled holes in the machine parts and these require a nut to tighten it from the other end.

Bolt heads

Bolts use a wide variety of head designs, as do screws. These are designed to engage with the tool used to tighten them. Some bolt heads instead lock the bolt in place, so that it does not move and a tool is only needed for the nut end.
Common bolt heads include hex, slotted hex washer, and socket cap.
These are held and turned by a spanner or wrench, of which there are many forms. Most are held from the side, some from in-line with the bolt. Other bolts have T-heads and slotted heads.
Screwdrivers are applied in-line with the fastener, rather than from the side. These are smaller than most wrench heads and cannot usually apply the same amount of torque. It is sometimes assumed that screwdriver heads imply a screw and wrenches imply a bolt, although this is incorrect.
Head designs that overlap both are the Allen or Torx heads; hexagonal or splined sockets. These modern designs span a large range of sizes and can carry a considerable torque.

How it is made?

Bolt head – Mainly formed by forcing the steel into various dies at high pressure.

Threading – Threads are formed by rolling or cutting.

Heat treatment – The bolt is exposed to extreme heat to harden steel.

Packing/stocking – After quality control to ensure uniformity and consistency, the bolts are packaged.
Bolts are one of the most basic components of engineering and construction, yet their production has become an advanced, high-tech process with multiple steps.

A summary of the production process:

1. Wire – Uncoiled, straightened and cut to length.
2. Cold forging – Molding the steel into the right shape at room temperature.
3. Bolt head – Progressively formed by forcing the steel into various dies at high pressure.
4. Threading – Threads are formed by rolling or cutting.
5. Heat treatment – The bolt is exposed to extreme heat to harden steel.
6. Surface treatment – Depending upon the application. Zinc-plating is common to increase corrosion resistance.
7. Packing/stocking – After quality control to ensure uniformity and consistency, the bolts are packaged.

8. Bolts can come in a wide range of different sizes and shapes, but the basic production process generally remains the same. Starting with cold forging steel wire into the right shape, followed by heat treating to improve strength and surface treating to improve durability, before being packed for shipment.
9.  “We do not produce catalog parts – everything we produce is custom-designed, according to the customer’s specifications,” says Henrik Oscarson, Technical Manager at Bulten’s production plant in Hallstahammar, Sweden. “Depending on where the fastener will be used, there are a number of different options for producing exactly the right bolt.”
10.  The grade of steel is standardized across the industry, according to the requirements of ISO 898 1. Using special tooling, the wire is then cold forged into the right shape. This is basically where the steel is molded, while at room temperature, by forcing it through a series of dies at high pressure.
11. For more complex bolt designs, which cannot be contoured through cold forging alone, some extra turning or drilling may be needed. Turning involves spinning the bolt at high speed, while steel is cut away to achieve the desired shape and design.
12. Heat treatment is a standard process for all bolts, which involves exposing the bolt to extreme temperatures in order to harden the steel. Threading is usually applied before heat treatment, either by rolling or cutting when the steel is softer. Rolling works much like a cold forging and involves running the bolt through a die to shape and mold the steel into threads.
13. Since heat treatment will change the properties of the steel to make it harder, it is easier and more cost-effective to apply to thread beforehand.
14. “The heat treatment can cause heat marks and minor damage to the bolt,” explains Henrik Oscarson. “For this reason, some customers demand threading after heat treatment, especially for applications like engine and cylinder head bolts.
15. For long bolts, where the length is more than ten times the bolt’s diameter, the heat treatment can have the effect of making the steel revert to the round shape of the original steel wire.
16. The choice of surface treatment is determined by the bolt’s application and the requirements of the customer. Often, the main concern for fasteners is corrosion resistance, and therefore a zinc-plated coating applied through electrolytic treatment is a common solution.  However, electrolytic treatment does come with an increased risk of hydrogen embrittlement.
17. When corrosion resistance is not an issue – such as inside an engine or an applying it regularly exposed to oil – using phosphate is a more cost-effective option. Once the surface treatment has been applied, standard bolts are typically ready to be packaged. However, more advanced designs may require some additional assembly, such as brackets.

18. Once these steps are complete, the bolt is finished. Now all that remains is some form of quality control to ensure uniformity and consistency before the bolts can be packaged and shipped.

Top uses of Bolt –

Bolts are often used to make a bolted joint. This is a combination of the nut applying an axial clamping force and also the shank of the bolt acting as a dowel, pinning the joint against sideways shear forces.
When secured together, the nut and the bolt are able to stay together without dropping apart due to the friction that is generated by their thread, compression of the parts as well as a slight stretch of the bolt.

The principal types of bolts commonly used include:
• Anchor Bolts
• Blind Bolts
• Carriage Bolts
• Double End Bolts
• Eye Bolts
• Hex Bolts
• Machine Bolts
• Penta-Head Bolts
• Round Head Bolts
• Shoulder Bolts
• Socket Head Bolts
• T-Head Bolts
• U-Bolts

Bolts are produced to a series of standards that assure uniformity in the dimensional characteristics and materials. When specifying standard bolts, the dimensional parameters should be designated per the tables of standards established by ANSI/ASME. These parameters include:
• Nominal size in fraction or decimal equivalent
• Number of threads per inch
• Overall length
• Material
• Finish

Types of Bolts and Their Uses
Head Shapes

Bolts, as well as screws, are available in a vast variety of head shapes. These heads are made in order to grip the tools that are used to tighten them.
The most common type of bolt head types includes square, hex, slotted hex washer and socket cap.
The earliest bolt heads in use were the square heads. Square heads consist of a square indentation on the head followed by a shaft that withstands rotation when a torque is applied to it.

There are numerous other head shapes in use as well, namely flat, oval, pan, round, button and truss.

Bolt Types

Anchor bolts Bolts with a threaded part in one end and a non-threaded L shaped part on the other. Usually found with a washer and a nut. Made to be rust-resistant.
Carriage bolts Fully threaded bolts with a smooth head and a square or ribbed undercut that prevents the bolt from turning when tightened. Fasten metal to wood.
Elevator bolts Fasteners with a thin flat or countersunk head and a square undercut that prevents the bolt from turning when tightened. Elevators and conveyor systems.
Eyebolts Rod-shaped fasteners with threads on one end and bent into a loop on another. Lifting applications such as wire and rope in light rigging.
It helps in the distribution of force from the bearing load. Also referred to as frame bolts. Frame applications such as truck and bed frames.
Hanger bolts Do not come with a bolt head. Both ends of the bolt are threaded. One of the ends is in the shape of a wood screw. In overhead applications and fastening metal to wood.
Hex bolts Bolts that are fully or partially threaded with six-sided heads. The broad range of use such as construction and repair of bridges, docks, highway elements, and buildings.

Lag bolts One of the toughest fasteners. It creates its own thread when it penetrates the wood and other soft material. Connect heavy materials that are bearing extreme loads.
Machine bolts Square heads paired with a semi-cone point and a fully threaded shaft.
Plow bolts Similar to carriage bolts. It contains a countersunk flat head followed by a square undercut and a threaded shaft.
Roof bolts Made of a shaft that is to be placed in a pre-drilled hole. Tunneling and underground mining. Provides support to the roof.

Consist of a long unthreaded, cylindrical shank that helps rotation of attached moving parts. Pulleys, moving engine parts, and mechanical assemblies, gears, and rolling wheels.
Squarehead bolts Consist of a square head, followed by a smooth shank and a machine screw thread. It can also be fully threaded with the absence of a smooth shank. The design of the head facilitates an easier wrench grip when tightening.
Step bolts Shank may be plain or textured. High strength, threaded bolts. Used as steps for climbing on steel communication and electrical transmission towers.
Structural bolts Are similar to the standard hex head bolts but have shorter thread lengths, in order to be used in structural applications. In all types of structural connections.
T-bolts Has a T shaped head in order to be held by a wrench or to be easily fixed in place. It provides a long-lasting connection. Use in buildings, instruments, furniture, automobiles, etc.
Timber bolts Sometimes referred to as mushroom head bolts or dome head bolts.
U-bolts Shaped like the letter U. Threaded on both ends and non-threaded in the curved section. Primary use to support pipework, especially pipes via which liquids and gases flow.

Bolts have markings to specify their strength, which depends on the material that the bolt is made up of and the dimensions that have been used to make the bolt.
Below is a table showing some typical materials via which common bolts are made and their corresponding markings. Materials mentioned are getting stronger progressively down the table.
Material Metric class marking Imperial grade marking

Top Bolt Fasteners Manufacturers And Suppliers In India –

• Sundream group, a leading name, with their corporate office in Noida has been in the infrastructure products and construction services, since 1967. Their brand name “Canon” is a leading brand in the fastener world, has just not come up on the Indian landscape and the International horizon in a day but is a prolonged, joint effort of the management and its team of workers.  They have 3000 plus product range for both home and industrial applications including nuts, bolts, plain and spring washers, road crash barrier fasteners, anchor foundation bolts, structural bolts, hot forged eye bolts, T-bolts, J-bolts, U-bolts, hexagonal nuts and bolts, threaded studs, forged fasteners and other customized components as per the drawing and requirement of the customer.
• Sundram Fasteners Ltd., Chennai: Started in the year 1966, is another name to reckon with in this high tensile fasteners field. They manufacture a wide range of high-quality fasteners for major precision-driven sectors like automotive, wind energy, aviation, aerospace, farm equipment and infrastructure sector.
• Daksh Fasteners in Ludhiana, Punjab: A client-centric company, established in the year 2010 are manufacturers, suppliers, and importers of a wide variety of fasteners like Hex bolts, foundation bolts, flat washers, threaded rods and studs, wing nuts, etc.

• Sterling Tools Ltd., Faridabad: With its presence since 1979, manufacture high tensile, high precision fasteners to fit Indian, German, Japanese, American, British standards, are leading suppliers across India, USA, Europe, and the Middle East.
• Kapsons India: Established in 1988, an ISO 9001:2008 certified manufacturer at their Kapsons Industries Ltd. Jalandhar plant is engaged in the manufacture of high-quality fasteners enjoying a vast Indian and global clientele in this field.
• GS Auto International Ltd., Ludhiana was established in the year 1974, a well-known manufacturer and supplier of fasteners to a wide range of Indian and International clients.
• Remax Fasteners Industries (India), Ludhiana: Is a renowned manufacturer of a complete range of fasteners for the heavy engineering, power and railway electric transmission sectors.
• Simmonds Marshall Ltd., Pune: Incorporated in 1960, manufacture a range of Specialized Nylon Insert Self Locking Nuts and other Special Fasteners to American, British, Japanese, ISO or Indian Standards catering to the Automotive and Industrial sectors and supplies to almost all the major Automobile Manufacturers in India and Abroad.

• Kova Fasteners Pvt. Ltd., Ludhiana: An ISO9001:2008 company is a leading manufacturer supplying to 29 nations world over a diversified range of fasteners.

Top Manufacturers And Suppliers In The World –
1. Ford Fasteners, Inc Hackensack, New Jersey
2. AALL American Fasteners, Cinnaminson, New Jersey
3. Crouch Sales Co. Inc, Dallas, TX
4. Liberty Fastener Company, Bensenville, IL
5. Hanger Bolt and Stud Co, Greenfield, IN

Bolts are used in all facets of human existence. Technically defined, a bolt is a threaded fastener that is intended for use with a nut. It can be made from many different materials: tempered steel, zinc, steel alloy, stainless steel, or brass, just to name a few. However, stainless steel bolts are limiting due to the possible incidence of galling. Galling occurs when two components actually fuse together. It can be caused by heat-treating or extreme temperatures.

Bolts can be either coarsely threaded or finely threaded. Each design has its advantages. In particular, coarse threads are preferred in high-speed assembly processes because they have less possibility of seizing. A fine threaded bolt is stronger and less likely to loosen; the smaller thread incline acts as an enhanced grip.

Many areas of manufacturing utilize only one type of bolt. Structural, carriage, flange and U-bolts are designed specifically for use in certain fields of industry. In suspension and similar areas of vehicles, the U-bolt (which is a U-shaped bolt that is threaded on both ends) is utilized. The carriage bolt is specifically meant to attach two-by-four legs to platforms. It can be easily recognized by the large round head and square neck. Finally, there is the flange bolt, which has a skirt of metal surrounding the bolt head to distribute the load of the bolt across the fastening surface. This increases the holding power by keeping the bolt from backing out of the surface.
It’s always a surprise when you learn something new or interesting about a subject you thought you knew everything about. Well fasteners are pretty cut and dry, right? Read on for a few facts about fasteners that may amaze you!

Fastener Fact 1
If you’ve ever designed a part with a tapped hole, you may have wondered, “How many threads do I need to make a strong connection?” The answer is that it varies, but six at most. Due to bolts stretch slightly when the load is applied, the loading on each thread is different. When you apply a tensile load on a threaded fastener, the first thread at the point of connection sees the highest percentage of the load. The load on each thread decreases from there, as seen in the table below. Extra threads beyond the sixth will not further distribute the load and will not make the connection any stronger.

Fastener Fact 2
There is a common misconception that black-oxide alloy steel socket head cap screws (SHCS) are ‘grade 8’. This is believed because grade 8 fasteners are so widely available that the label has become associated with all high-strength fasteners. Technically speaking, to be considered ‘grade 8’, a fastener has to meet industry standards for various characteristics. Three of the most important physical properties of SHCS are inconsistent with the ‘grade 8’ classification: tensile strength, hardness, and markings on the bolt head. SHCS is actually stronger than ‘grade 8’, and have more in common with grade 9 fasteners.
Fastener Fact 3
When a bolted connection will be subjected to a fatigue loading, you want to tighten the bolt up to its yielding point for maximum strength. A bolt will experience zero change in load if the applied tensile force is less than the compressive force of the connection. So, a tightly fastened connection is better suited to withstand fatigue loading than a loose connection because the bolt itself will not sense the fatigue load, only the constant force applied due to the clamping of the joint. To ensure that the connection is properly fastened, you can look up the recommended torque for a given fastener type in a table like the one found here. If the applied torque is critical for your application, make sure that you apply the recommended torque to the head of the bolt, rather than the nut. Torquing the nut can result in different nut factors and change the torque required to achieve proper pre-load.
Fastener Fact 4
Have you ever seen a fastener labeled with a 2A or 3B rating and wondered what that meant? That number-letter combo is used to indicate the thread class of the fastener. Thread classes include 1, 2, 3 (loose to tight), A (external), and B (internal). These ratings are clearance fits which indicate that they assemble without interference. Classes 1A and 1B are rarely used but are a good choice when quick assembly and disassembly are a priority. Classes 2A and 2B are the most common thread classes because they offer a good balance between price and quality. 3A and 3B are best used in applications requiring close tolerances and a strong connection. Socket cap and socket set screws are usually class 3A.
Fastener Fact 5
All fasteners are available with either coarse or fine threads, and each option has its own distinct advantages. Finely threaded bolts have larger stress areas than coarse bolts of the same diameter, so if you are limited on the bolt size due to dimensional constraints, choose a fine thread for greater strength. Fine threads are also a better choice when threading a thin-walled member. When you don’t have much depth to work with, you want to utilize their greater number of threads per inch. Fine threads also permit greater adjustment accuracy by requiring more rotations to move linearly.
On the other hand, coarsely threaded bolts are less likely to be cross-threaded during assembly. They also allow for quicker assembly and disassembly, so choose these when you will be reassembling a part often. If the threads will be exposed to harsh conditions or chemicals, a coarsely threaded fastener should be considered for its thicker plating or coating.
Fastener Fact 6
When designing a clearance hole for a bolt, it helps to refer to a chart to pick the correct hole size. A useful reference can be found here. Similarly, when pre-drilling a hole that is to be tapped, it helps to have a chart to refer to the appropriate size pilot hole. Such a chart can be found here.

 

 

 

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