A bolt is a type of fastener that, like all fasteners, is used to fasten or secure materials together. There are many kinds of nuts and bolts, and the majority, if not all, have machine threads when it is a screw type.
A threaded bolt inserts into nuts and joins parts together, or fastens materials together. The types of bolts (just a few) would be eye bolts, wheel bolts, and machine bolts. This guide will also show you various bolt Types.
Types of bolts
These are different types of bolts:
- Anchor Bolts
- Arbor Bolts
- Blind Bolts
- Carriage Bolts
- Elevator Bolts
- Eye Bolts
- Flange Bolts
- Hex Bolts
- J-Bolts
- Lag Bolts
- Machine Bolts
- Hanger Bolts
- Plow Bolts
- Rock Bolts
- Serrated Flange Bolts
- Sex Bolts or Chicago Bolts
- Shoulder Bolts
- Socket Head Bolts
- Square Bolts
- Stud Bolts (Double end stud bolts, tap end stud bolts)
- T-Head Bolts
- Tap Bolts
- Toggle Bolts
- Track Bolts
- U-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.
Anchor bolts are used to connect both structural and non-structural elements to concrete.
The connection can be done with several types of components, anchor bolts, steel plates or stiffeners. Anchor bolts convey different types of loads, tensile and shear forces.
The connection of structural elements can be represented by steel columns connected to a reinforced concrete foundation.
A common example of a non-load bearing element attached to a structure is the connection of a facade system to a reinforced concrete wall.
#2. Arbor bolt.
Arbor bolts are a specific type of bolt, designed for use in tools typically used by mitre saws and keep the tool fixed and the blades in place.
An “arbor” is the shaft that holds the blade. On all American stationary saws using a 10 “blade, the arbor is more than 5/8” diameter (the part where you attach the blade).
Arbor bolts are different than any other bolts because they arrive pre-assembled. All arbor bolts (the bolt) have a washer that is permanently attached to the tip of the bolts.
The enclosed washer is one of the very first ways that Arbor bolts have a distinctive look or style. Arbor bolts also have a sunken head which creates a ridge around the outside edges of the bolt head.
Arbor bolts are typically black or dark in color.
Arbor bolts are also made with reverse thread patterns.
Looking at the shaft of an arbor bolt, it at first glance appears to be backward with an inverted thread pattern like other bolts but this reverse thread is part of the function of the arbor bolt.
#3. Blind bolts.
A blind bolt is a structural fastener offering greater strength and conformability over a standard rivet or weld.
Blind bolts were designed to create a strong connection where traditional rivets or hex bolts were complicated to assemble or were incapable of doing the job.
Typically, in cases of restricted access, using blind bolts is often the only option available to complete the specific connection, which is precisely why they were invented.
The effectiveness of the blind bolt fastening system provides confidence to manufacturers, builders and repairers that for decades blind bolts would likely be their first choice in constructions or repairs made in restricted access.
#4. Carriage Bolt.
Carriage bolts are a type of bolt designed to fasten metal to metal or more commonly wood to metal. Carriage bolts may also be referred to as washer head screws in Australia and New Zealand.
The carriage bolt is distinctive because of its flat mushroom head and the fact that the cross-section of the shank is circular for most of its length, however it is square just below the head.
This means once inserted through a square hole in a metal band, it is fairly self-locking, allowing the fastener to be mounted from one side with one tool (a wrench).
The head of a carriage bolt is typically a flat dome shape and the shaft has no threads, with the diameter of the shaft corresponding to the side of the square cross-section.
Carriage bolts were designed to be bolted through an iron reinforcement plate on either side of a wooden beam, with the square portion of the bolt fitting into a square hole in the ironwork.
It is common to use carriage bolts on bare wood, where the square section gives enough grip to the fasteners to eliminate rotation.
Carriage bolts are often used in securing fastenings, such as locks and hinges, where the bolt only needs to be removable from one side. The smooth domed head along with the square nut beneath is designed to prevent the carriage bolt from being unlocked from the unsafe side.
#5. Elevator bolts.
Elevator bolts are threaded fasteners that have a thin body with a round head. Elevator bolts have either a square neck or ribbed neck to stop the bolt from turning when the nut is tightened.
Elevator bolts are used in confined spaces with moving componentry such as elevators and conveyor belts. Because they have a thin head that allows them to fit flush to the mating surface of the component, elevator bolts will not interfere with small or confined operational systems.
#6. Eyebolt.
Eyebolts are mechanical fasteners that consist of a threaded shaft and a head that forms a ring. Eyebolts are designed to attach to an eye to a structure (i.e. eye of a shackle), allowing rope or cable connections.
One of the significant applications of eyebolts is to create a lifting eye so that a crane can be attached to machinery with specially designed lifting eyes identified for their safe work load.
Low-strength eyebolts are typically formed from a single length of bar stock with the diameter of the nominal diameter of the thread size. The head is bent into a ring from and unthreaded section of the bar body. The types of eyebolts can carry axial loads reasonably well although they should not be subjected to any type of off-axis loads or forces.
The opening created where the end of the bar is completed to form a ring may be welded although it is likely to remain a potential failure point.
#7. Flange Bolts.
Flange bolts have a circular flange under the head which is an integrated washer that distributes the load. Non-serrated flange bolts are sometimes referred to as frame bolts.
Flange bolts are used in automotive applications, plumbing and many more. Flange bolts have a washer-type flange under the head of the bolt that both speeds production time and will distribute the clamping load while providing protection to the mating surface.
If you are wanting a reliable and long-lasting connection between, say two sections of an enclosed large area, then you will need to incorporate a flange bolt; examples include, the connection between the transmission and engine in a vehicle.
#8. Hex Bolt.
Hex bolts and hex cap screws have a hex head that is used to tighten the fastener. A hex bolt has washer under the head and a beveled end. Hex cap screws do not have either feature and utilize a nut.
The fasteners are extensively used in construction, machine parts, and maintenance repair. Hex cap screws and hex bolts are made in several sizes, finishes, quality, and materials for different applications.
#9. J-Bolts.
A J bolt is a bolt shaped like the letter J, and can be used for many applications. Even though J bolts do not have a bolt head, they can accept a nut on the threaded end. J bolts can be found in the construction industry.
J bolts can be cast as an anchor bolt in a concrete slab using the bent end. J bolts are commonly used to secure walls in concrete and roofing applications.
Almost all hardware and building suppliers stock J bolts, and custom sizes can also be ordered from manufacturers of bolts and fastening products.
J bolts are typically manufactured from different metals and exposed to different treatments for different uses and applications. It can be useful for do-it-yourselfers to have a few j bolts laying around for miscellaneous projects.
#10. Lag Bolts.
Lag bolts or lag screws are technically screws because they don’t accept a nut. These incredibly strong fasteners are usually used to assemble heavy lumber or other heavy materials that are under extreme loads.
Lag bolts are different from standard wood, self-drilling, or sheet metal bolts. In relation to most common bolts, they are HUGE! Most lag bolts are at least one inch long and ¼ inch thick.
An example of screws are wood screws, which are used to secure an application that consists only of wood materials. Wood screws are coarse threaded, but the threading does not span the entire length of the fastener.
#11. Machine bolt.
Machine bolts are used to connect two dissimilar pieces of material and are like hex bolts, but they do not contain a chamfered point nor a washer-support surface on the underside of the head. They are usually available in a hexagonal and square head.
Another fastener, machine screws is commonly interchanged with machine bolt and creates confusion. Machine screws are usually smaller than machine bolts, however, they are fully threaded along with the length of the fastener.
Unlike wood screws, sheet metal screws, or other types of screw fastening devices, machine screws are designed with a flat tip (not a pointed or conically shaped tip, which is common when comparing to a screw to a fastener).
Screws are mostly designed to be installed with pre-drilled holes or to be installed into material where the screw creates the thread when torqued tight.
Bolts on the other hand are designed to be tightened by applying and torquing a mating nut onto the end of the bolt. Although a “nut” and a “bolt” have two paired fasteners, a nut is typically not used with bolts that are threaded into pre-drilled holes.
Machine bolts are available in many head styles, including hex head, which is typically mated with a hex nut, as well as flathead, oval head, and cheese head, to name a few.
#12. Hanger Bolts.
A hanger bolt is a double-ended bolt that is primarily utilized to add legs to furniture. Hanger bolts are very much an unsung hero of hardware.
These bolts aren’t stylish, they aren’t beautiful, and you might never hear about them or think about them. But hanger bolts are not like those other bolts that are constantly parading around in front of you, but hanger bolts do so much for your home.
You see, hanger bolts primarily attach legs to furniture. So once you really start looking, you will see that hanger bolts are right above you, and all around you every day. If you are going to put a piece of furniture together then you need to know everything about hanger bolts.
#13. Plow Bolts.
Plow bolts are used to secure the plow share (blade) to the frog (frame), and let the earth pass over their heads without interference to the moldboard. They are also used to fasten the blades of bulldozers and motor graders.
Plow bolts have a small round countersunk head, and a square neck – the width of the square (measured across the flats) is equal to nominal diameter of the bolt.
The head can be flat (for plows), or dome (convex) shaped (for dozers/graders), The conical (tapered) bearing surface of a plow bolt is 80°.
#14. Rock Bolts.
A rock bolt is a long anchor bolt, used for stabilizing rock excavation which may be used in tunnels or rock cuts. It transfers load from the unstable exterior to confined (and much stronger) interior of the rock mass.
Rock bolts are almost always installed in a pattern, the design of which depends on the rock quality designation and type of excavation. Rock bolts are an integral part of New Austrian Tunneling method.
Like anchor bolts, there are many proprietary designs for rock bolts, with either a mechanical or epoxy method of establishing the setting.
There are also fiberglass bolts that can be cut through again by subsequent excavation. Many papers have been written on the methods of rock bolt design.
#15. Sex Bolts or Chicago Bolts.
Sex bolts are fasteners made up of a barrel shaped female component with internal threads that covers the threaded male component. The female part is the nut and is of the same length as the male portion.
Each component has a flange as the bearing surface and makes the connection surface more even. Sex bolts are well-suited for fastening materials that can be damaged by abrasive parts.
Examples of use of sex bolts include paper binding, helmets, railing systems, furniture, playground equipment, signage, bathroom partitions, and other products.
#16. Shoulder Bolts.
Shoulder bolts, or shoulder screws, have a shank with a larger diameter immediately below the head that “steps down” to a smaller diameter for the length of the thread.
The change in diameter produces a “shoulder” that can be tightened against the part that screws on. This allows a shoulder screw to be firmly attached to one part without clamping the other part, thus creating an axial clearance.
The shaft gives the connection a smooth bearing surface for the bolt connection between the parts. Shoulder screws can be used with a sliding bearing like a nylon bushing to facilitate improved rotation between the parts.
#17. Socket Head Bolts.
Socket cap screws are machine screws with a cylindrical barrel shaped head containing a hexagonal socket. The head of a socket cap screw is smaller in diameter than most other machine screw heads, usually only extending 1.5 times the nominal thread diameter.
Socket cap screws have other names as well – socket head cap screws, cap head socket screws, or hex socket head screws.
These components do not require external clearance for fastening, as hex head screws do to accept a spanner or socket. These properties mean that socket head cap screws are good to use when space is limited.
# 18. Square Bolts.
Prior to hex bolts becoming standard equipped, square head machine bolts were the industry standard.
Today, square bolts are typically used for aesthetic reasons that offer a rustic look to a new structure, or to remain consistent with existing fasteners in an older structure. Square lag screws are also an aesthetic choice for similar purposes.
# 19. T-Head Bolts.
T-Head bolts are mostly used with a nut to join an object that has a T shaped slot, so that the head of the bolt can be put flush, or sub-flush, to the material surrounding it.
T-head bolts are used in several applications, including machine tool clamping fixtures, and pipe clamps.
The bolt can be installed into the T-shaped slot and locked in place with a 90° turn because of the T-head configuration.
# 20. U-Bolts.
A U-bolt is a bolt shaped like the letter U that has screw threads on both ends.
U-bolts main reason for use is for supporting pipework, and pipework that transfers fluids and gasses.
U-bolts can sometimes be a bit eccentric in their measuring system, as they were measured to support pipe-work engineering terms, and would be requested in regard to the size of the pipe it was supporting. U-bolts are also used for other applications, such as rope together.
So for example, a pipework engineer might requisition a 40 Nominal Bore U-bolt and there would be no way of them knowing what it was! The 40 nominals bore has little resemblance to the actual sizes and dimensions of a U-bolt.
The nominal bore of a pipe is actually measurement of the inside diameter of the pipe. Pipework engineers were/are concerned with this size because they design a pipe based on the amount of fluid/gas it can transport.
Since more and more manufacturers are using U-bolt fastener systems, and the public is, users of U-bolts should use a more accurate measurement system.