20 Different Types of Bolts and Their Uses

Bolts represent a significant subset of fasteners that are widely used to connect or hold parts together. In fact, fasteners to generally connect or hold materials together. Bolts are an important part of a group that contains many varieties that fulfill many different purposes.

Most bolts, just like other screw-type fasteners, have manufacturers machine threads that allow them to be fastened securely to the corresponding nuts. The thread standard enables different components to be attached securely.

Different bolt types and applications include: eye bolts, wheel bolts, and machine bolts. If you are trying to learn bolts and their applications, this guide introduces the various industrial types, and common applications clearly and simply.

Types of bolts

These are different types of bolts:

Below are summaries of each of these common types of fasteners and a description of their important characteristics and uses.

Related posts: Different types of Nut and Bolts

1. Anchor bolt

For fastening pushers in both structural and non-structural concrete, anchor bolts are the primary connection. While an anchor bolt connection may only consist of bolts, there are often other elements involved, such as, steel plates or stiffeners per the design condition. Anchor bolts serve a functional purpose because they are typically subjected to a combination of tension and shear loads.

For example, similar to example 3, an example of a structural connection with anchor bolts would be steel columns anchored to a reinforced concrete foundation.

For example, a common example of a non-load-bearing element is attaching a facade system to a reinforced concrete wall. Although there are no structural loads imposed on these components, it is still important to provide a stable anchor connection.

2. Arbor Bolts

Arbor bolts are specifically designed fasteners, intended mainly for use with power tools, mostly with miter saws. Their primary purpose is to hold the tool securely and keep the blade in a rigid position during use.

In this instance, the arbor means the shaft that supports the blade. For most stationary saws in the United States that have a 10-inch blade, the arbor is most often 5/8 inch diameter where the blade attaches.

One of the unique characteristics of arbor bolts is that they are preassembled. Also, all arbor bolts have a washer that is permanently attached to the end of the bolt.

This built in washer not only facilitates installation but gives arbor bolts a look that is instantly recognizable when pulled from the box. There is also the dimension of the recessed, or sunk head as compared to other bolts, which has a raised edge or ridge right around the head, another distinctive visual trait.

When it comes to materials and finishes, the most common finish for arbor bolts is in dark black, which contributes to their structural properties and durability, as well as their physical identity. Arguably, the most functional feature is the threading: arbor bolts are made with reverse or left handed threads.

Upon first appearance, the threading of the arbor bolt may seem strange, “backward,” or unusual when compared with bolts you have seen before, because of the inverted thread pattern.

The reverse thread is not just a frivolous design characteristic as it serves a vital functional need, which is to keep the bolt tight once it is fastened in place for use. In applications where the blade spins and rotates, a traditional threaded bolt might become loosen over usage.

3. Blind bolts

Blind bolts are a type of structural fastening device that has been designed to be more reliable and work in more conditions than traditional fastening methods like rivets or welding.

Blind bolts were created as a fastening device in applications where traditional rivets or even hex bolts could not be used very simply due to access to the fastening location.

Blind bolts are meaningful in many situations, when making “true” or even “alternative” fasteners, such a rivets or hex bolts, are just impossible to work with. This defines blind bolts.

Blind bolts function and provide effective means of securing structural elements, and have been in use, especially in manufacturing or in construction and structural repair for several decades in activities that involve in restrictive work environments where access to the fastening location is limited.

4. Carriage bolt

Carriage bolts are a specialized fastener that can be used to join metals to wood, or for metal-to-metal connections and is commonly referred to as a washer head screw in regions such as Australia or New Zealand.

In regards to what makes this bolt special compared to other bolts, is its flat, mushroom-shaped head and square neck under the head and the rest of the shank is round like most bolts.

The square neck is important because when the bolt is placed in a square hole (usually in a metal strapping or plate) it locks itself in place.

The square neck means the carriage bolt can be installed from just one side with only a wrench or a spanner, making it easier to assemble.

Usually, the head on a carriage bolt is a smooth dome and the area beneath the head is unthreaded (table D) and is the size of the square neck. The unthreaded area contributes to a better fit.

Originally carriage bolts were designed to go through iron reinforcements on both sides of a wooden beam. When tightened, the square neck would fit into a matched square hole in the iron and aid in sustaining the joint without allowing the bolt to spin.

However they are often also used directly into bare wood as the square neck bites into the wood enough to prevent the bolt from rotating.

Carriage bolts are also recognized as a fastening element for various security objectives for example, door locks or safety locks, or hinges.

The smooth rounded secure head will prevent turning or gripping from the insecure, visible side, while the square neck and nut will not be visible or accessible until the secure side is used or dismantled.

5. Elevator bolts

Elevator bolts are a class of threaded fastener defined as having a flat and round head and a thin shaft, sometimes with a square or ribbed neck below their head that prevents rotation when the nut is tightened.

Elevator bolts are good to use inside tight mechanical confines, such as an elevator or conveyor systems, where attaches components are moving.

Elevator bolts are good for limited space applications because their low-profile head can sit nearly flush or above the surface being attached. In applications where the mounts may interfere with operating surrounding parts, even a small amount can create issues.

6. Eyebolt

An eyebolt is a category of mechanical fastener that has a threaded stem and a head formed in a loop or ring shape. It is frequently utilized when one wants to form a secure point of attachment on a structure for safely attaching ropes, cables, or shackles.

Eyebolts are quite often used for lifting, or in the case of hoisting, eyebolts serve as the clearing devices that cranes or lifters hook onto machinery, etc.

The eyebolts in these cases are special, below an appropriate lifting eyebolt’s stem, will be a rating indicating the acceptable working load limit to which the eyebolt can be attached and subsequently relied upon for safe lifting.

For lesser strength applications, eyebolts can sometimes be made with a straight bar, with the nominal thread diameter of the diameter. The head is usually formed by bending the unthreaded end of the bar.

Although they are more than capable of supporting axial or parallel loads applied in-line with the eyebolt’s shaft, they are generally not as capable to hold angles or loads off-axis to the bolt and therefore there are limits to their strength.

Within some designs, the head is actually closed by welding the point where the two ends of the bar connect.

However, even when the bar is welded at the head it can still serve as a potential weak joint where it may fail under applied loads however this depends solely on the level of applied working load acting on the specific weld and how it is manufactured and used.

7. Flange Bolts

Bolts with a flange design have a circular flange just below the head of the bolt; therefore, functionally the same as a built-in washer. This design helps disburse the load when tightened. If the flange is smooth instead of serrated, these are generally called frame bolts.

Flange bolts are widely used in many applications, especially in automotive and plumbing applications. The built-in flange decreases assembly time since there are no separate washers to insert, while disbursing out the clamping force and protecting the surface underneath the head of the bolt from damage.

When considering the attachment of two major, enclosed components, such as connecting the engine to the transmission in a vehicle, a flange bolt is necessary. The secure hold and durability help maintain a strong joint for demanding structural connections.

8. Hex bolt

Both types of fasteners have a hex head, which means they have a six-sided head that can be tightened with a wrench or socket.

The primary difference is that hex cap screws have a washer face beneath the head of the screw, whereas hex bolts typically do not, and hex cap screws usually have a chamfered (beveled) end that assists with alignment when installed. Hex bolts essentially need a nut on the other end in order to lock it down.

You may notice them in numerous situations, from construction sites to machinery assembly to the occasional repairs. They come in many sizes, finishes, grades, and materials that are selected based on the specific task needing completion.

9. J-Bolts

A J-bolt is a fastener shaped like a “J”, and is utilized in the construction and industrial trades in a variety of ways. A benfit of a J-bolt is that it is easily understood as it doesn’t have an exact bolt head and has a threaded and nut ready end.

The most common use of a J-bolt is in the construction industry for anchoringJ-bolts are housed in concrete slabs and act as anchor bolts, while the curve is encased in the slab. J-bolts are useful for anything from holding walls to how much roofs are supported.

J-Bolts can easily be found at almost every building supply and hardware retail operation. They can also be special ordered through the manufactures that the retailer works with if the J-bolts are not found as a specific length or type of material.

Based upon the make and use of the J-bolt there can be varying types of metals and some types have surface treatment during the manufacturing to increase its durability and performance. You probably do a fair amount of handyman work and its always good to have a couple of J-bolts, the reality is you will fined a use for them.

10. Lag Bolts

Lag bolts are often referred to as lag screws but as they do not work with a nut to serve their function, they are classified as screws rather than bolts.

Lag bolts are specifically designed for strength, and durability, making them the fastener of choice when the need arises to join heavy lumber or load-bearing materials. Lag bolts are appropriate in situations where a stable application is required and significant strains are going to be implemented.

Compared to standard wood screws, self-drilling screws or sheet metal screws, the size and strength of the lag bolt is the type of fastener.

Lag bolts are much heavier and stronger than standard bolts as many are at least one inch long and about a quarter inch thick. This added size enables lag bolts to tolerate much more stress and all of these factors contribute to why they are very commonly utilized in structural applications.

For comparison, consider wood screws. Wood screws are normally used to attach wood to wood. Wood screws have large threads, to grip wood securely, however, these threads usually do not extent the entire length of the screw. Lag bolts are a better solution to provide a secure and lasting solution when wood screws cannot be used.

11. Machine bolt

Machine bolts are used for fastening two separate pieces of material together. Although machine bolts can look the same as hex bolts, they fundamentally differ by the fact that machine bolts do not have the chamfered point of a bolt or the washer-bearing surface below the head typically found on a bolt. 

Machine bolts will also typically be either hex or square headed but allow for some variability in applications. 

There is also a common misunderstanding of machine bolts versus machine screws, as both terms are often confused and sometimes used interchangeably. The largest difference between the two is their size and how they are threaded. 

Machine screws are normally smaller and threaded uniformly for their entire length while machine bolts are typically larger and are threaded differently. 

Unlike wood screws or sheet metal screws which have points or tapered ends designed to penetrate material, machine screws and machine bolts have flat tips. Flat tips when combined with the diameter often makes machine screws and bolts better suited to the material where their flat tips aid to predrilled holes or formations in the own threads as it is secured into softer materials. 

Another basic differentiation is how it is secured. Generally bolts should be fastened with a nut which will be torqued onto the threaded end which will make it secure. 

However, not all bolts require a nut; there are bolts that are going to be fastened into tapped holes where the bolt is threaded directly into the material meaning the nut and further unnecessary application. 

There are other head styles other than hex and square for both machine bolts and machine screws to suit the application. Machine screws and bolts are used in normal applications with flat, oval, and cheese head etc. and hex nuts are commonly used with the hex-headed bolts.

12. Hanger Bolts

A hanger bolt is a type of double-ended fastener that is frequently used in the assembly of furniture for attaching legs to a variety of furniture types, although it generally doesn’t seem to get the same level of attention. Still, whether furniture enthusiastially or not, hanger bolts are crucial to the structural integrity of a multitude of items in the household.

Hanger bolts are not style or decoration statements, and if we’re being honest, most people probably never notice them. However, without hanger bolts, much of what we rely upon on a daily basis would quite literally fall apart.

Take a look at the furniture around you – tables, chairs, desks, etc, and there is a good chance that those items use hanger bolts that are quietly doing their job of holding it all together!

If you’ve ever tried your hand at assembling furniture on your own, you’ve likely encountered a hanger bolt, whether you were aware of it or not, fincluding in the case of attaching legs! Understanding how hanger bolts work will not only make the process of assembling furniture easier but actually safer and more reliable!

13. Plow Bolts

Plow bolts are critical components used to fasten a plow share (or blade) to a frog, which is the main body of a plow. Plow bolts are designed to work in conjunction with moldboards since they are flush with the face so that soil slides freely over them without interfering with the work of the moldboard.

Plow bolts are used to fasten more than just plows. You will often find them fastening blades on heavy machinery such as bulldozers and motor graders.

The unique aspect of plow bolts is their shape with a small round countersunk head and a square neck. The flat of the square neck (measured across the flat) is nominally the same diameter as the bolt.

The head of the bolt is flat (common for plows) or dome-shaped (slightly convex), which is common with dozers and graders, depending on the application.

An additional technical note is that the conical bearing surface of the head is tapered at an angle of 80° so that it fits properly in its countersunk hole.

14. Rock Bolts

A rock bolt can be considered a long anchor, and essentially works to support rock masses, particularly during excavation (such as tunnelling or open rock cuts).

The main concept in utilizing a rock bolt is transferring the force/load from weak, potentially unstable outer layers of rock to the stronger, more stable inner layers. When used correctly, rock bolting can stabilize your excavation and rock mass.

Rock bolts are not installed sporadically; rather they are installed based on certain patterns/specifications according to the rock quality designation (RQD) and type of excavation.

Rock bolts are a significant component of the new Austrian tunneling method (NATM), which emphasizes stabilizing the surrounding rock, rather than resisting it.

There are a variety of rock bolt systems available. Some work using mechanical expansion, and others utilize epoxy and resin. In certain situations, such as when future excavation is planned, fiberglass bolts are commonly utilized; they have the ability to be cut without significant effort.

There has been substantial research in rock bolt design, and many technical papers have contemplated the different designs and approaches to optimize rock bolts.

15. Sex Bolts or Chicago Bolts

Sex bolts are fasteners with two components; a female barrel-shaped part with internal threads and a corresponding male part with external threads.

The female part is the nut part and is usually constructed to be the same length as the male part so that it fits properly. Both parts have a flange, which provides a bearing surface which distributes pressure better but also creates a clean connection point.

Having the connection point as clean as possible is especially important when fastening materials that may be damaged through rough or sharp hardware.

Sex bolts are designed specifically for fastening delicate, or finished surface materials and are utilized in products that you probably interact with regularly, such as bookbinding, helmets, handrails, furniture assembly, playground structures, installations, bathroom partitions, etc.

16. Shoulder Bolts

Shoulder screws, also known as shoulder bolts, differ from other screws in that their shaft area below the head is larger than the throated or shank portion. This size differential creates a “shoulder,” or clearly demarcated area where the diameter of the screw transitions from large to small.

This shoulder has a function it allows the screw to be anchored to one part without resting directly on the other part. This creates an intentional axial clearance, which is especially beneficial when parts move or intentionally separate from one another as in an assembly.

The unthreaded part of the shaft provides a bearing interface having a smooth and constant surface. Often, shoulder screws are used with sliding bearings such as nylon bushings, where rotational cadence and any degree of separation are more desirable in order to avoid failure of the mating components, as well as to function properly when assembled.

17. Socket Head Bolts

Socket cap screws can be characterized as a type of machine screw that have barrel shaped, round heads that recess to a hexagonal hex socket at its center.

Whereas a majority of machine screw heads are much larger than the nominal diameter of the threaded shaft, these heads are only slightly larger than the nominal diameter, often about 1.5 times larger.

They may also be referred to as socket head cap screws, cap head socket screws, or even hex head socket screws depending on the context or region.

One major benefit is that unlike hex head screws that require the use of a spanner or socket which requires extra space around the head, socket cap screws do not require the extra space because the shape of the cylindrical head can be inserted into spaces with limited space.

This makes them particularly useful in tight spaces where standard fasteners may be entirely impractical.

18. Square Bolts

Before the prevalent use of hex bolts, square head machine bolts were the industry standard in many fields. These bolts have since been mostly replaced, other than use in aesthetic situations, they still remain valuable.

In some cases square bolts are selected to add rustic aesthetics to new structures or to provide a historic or traditional look that would align with and older building that maybe originally included square head bolts. Similarly, square lag screws are sometimes used to keep or replicate a traditional aesthetic where appropriate.

19. T-Head Bolts

T-head bolts are made to be used in combination with a nut to hold components in a T-slot when fabicating or installing. T-head bolts permit the shape of the head to sit flush with the surroundings or be slightly recessed.

Frequent uses of T-head bolts in the real world are machine tool clamping fixtures and pipe clamps. Examples of how T-head bolts can be fabricated or installed can sometimes be seen in designs used in university or engineering schools.

The T-head design is convenient, as the bolt head can be inserted into the T-slot, then rotated 90 degrees to lock it into position. This can be easily done by hand, with no tooling or complicated assembly.

20. U-Bolts

A U-bolt is a type of fastener that is formed in the shape of the letter “U” with a leg threaded on each end that can be locked in place by nuts.

Until now, U-bolts have been touted as the standard fastener for supporting piping systems, specifically the tube-like objects that convey liquids or gases. Historically, because of U-bolt’s roots in pipework engineering, it was usually described with terminologies that were familiar only to pipework engineering.

For example, instead of describing the physical sizes of U-bolts, the engineer would simply refer to the U-bolt with reference to the nominal bore size of the pipe it is intended to support.

If someone asked for a “40 Nominal Bore U-bolt,” it made complete sense to a pipework engineer, even though, 40 bore does not resemble any dimension of the U-bolt.

As mentioned previously, nominal bore refers to the internal diameter of the pipe and is not limited to the physical external dimensions of the pipe.

For design purposes, engineers are concerned with the internal diameter as it dictates how much fluid, or gas can flow through the piping system, and their goal is to create a system that optimises flow efficiency.

The modern use of U-bolts are certainly not limited to industrial piping. U-bolts are now finding themselves being used for all types of purposes including securing round bars to clamping down tubing parts where engineering does not play a role.

Because of this transition away from the piping traditional materiality, the historical and specialized means of sizing a U-bolt is not convenient for a non-historically based version of users.

As U-bolts continue to evolve past that of a pipe support element, it seems wise to adopt a more basic and common method of measuring and defining a U-bolt.

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