In our last blog, we discussed the many attributes of fasteners: shapes, materials, coatings and plating, different heads, and drivers. Now, the actual fasteners themselves!
Fasteners come in diverse types, given the limitless applications. Each of those types also has many subsets. Among the numerous types of fasteners, here are many of the most common ones.
Bolts are one of the more common threaded fasteners used to hold two non-threaded pieces together. A bolt head, which comes in several varieties, is attached to the threaded male end. Their shape and type of head classify bolts. They have a flat head which means there is no grove on the head. These are usually used with a nut or a washer to hold the material in place. Examples include:
Anchor bolts are referred to as “cast in place,” which means they are included in the fabrication of the component or part and are permanently attached to it. Diverse types of anchor bolts are designed for specific jobs. They are industrial bolts embedded into concrete for securing columns and foundations’ support.
Arbor bolts have a washer permanently attached to the head and reverse threading. The head of an arbor bolt has a sunken design that creates a ridge on the head. Most arbor bolts have a dark or black finish that distinguishes them from other bolts. They are designed to be used with tools such as a saw to keep the blade in place.
Carriage bolts have a smooth head with a square section underneath that keeps the bolt from turning when secured. The popularity of carriage bolts is due to their ability to be used with any material, from stainless steel to wood. They are referred to as plows or coach bolts and get their name from their original use, which was to secure carriages and carriage wheels.
A double-end bolt has threads at both ends without a head. They can have a nut on one end and insert into a threaded hole. Double-end bolts can be further sub-categorized by various types.
Eye bolts have a loop or circular configuration instead of a head. The eye or loop secures electrical lines and holds chains or guide ropes. The loop end can be opened or closed; the available version does not have a completed loop, while the closed version does.
The hex head bolt gets its name from its head’s hexagonal shape, which makes it easy to tighten using a wrench. The six sides of the hexagonal shape give the bolt the proper granularity angles for fastening the bolt under challenging locations. The threads on a hex head bolt extend halfway or up to the bolt head, with partially threaded bolts having a higher shearing capacity.
U-bolts have two threaded arms connected by a U shape bend without a head. The threaded ends are designed to connect nuts and washers. They are made from carbon, alloy, or stainless steel by cold or hot forging. When the washers and nuts are tightened, they provide clamping force to connect parts or to hold components in place and prevent them from moving.
A pin fastener is usually a rounded piece of metal that joins two separate, hinged objects together. Pin fasteners are primarily used to secure or connect parts. The main forces acting on them are shear, opposing forces pushing one section of the pin in one direction and another in the opposite direction.
The common types of pins include:
A dowel pin is simply a cylinder of solid material inserted through a hole. Typically, the hole has a fit so that compression of the pin and the resulting friction holds the pin firmly in place. Dowel pins also usually have a chamfered end to enable insertion.
The slotted pin is formed from sheet material rolled into a partial cylinder with a chamfer at each end. The chamfer allows the pin to be forced into a hole smaller than the pin’s relaxed diameter. The gap in the cylinder allows the pin to compress to fit into the hole.
A coiled pin is like a slotted pin, but the sheet material is coiled by more than a complete revolution. A coiled pin is, therefore, more heavy-duty than a slotted pin. Slotted and coiled pins rely on spring force. The pins are designed to compress, exerting a spring force against the sides of the hole.
A grooved pin is a solid pin, typically steel, with three grooves swaged along its length or a part of its length. This pin style creates a pin with more elasticity than a solid dowel pin but more robust than a spring pin. These pins are also driven into a tight hole.
Split pins are a type of pin bent in half so that its installer may insert both ends through the same hole. They are typically manufactured from a half-circular profile so that the two ends together form a circle which fits into the hole. The bent end is formed into an enlarged end, and the double end can be bent outwards to prevent the pin from being removed.
These threaded fasteners create their threads while fastening into the material. They typically have a head and a shank with a helical thread. They have several types of head styles and drive styles (see the previous blog).
A dowel screw is like a double-end bolt with both ends threaded with a wood screw tip. They do not have a head and can be inserted into pre-drilled holes or create their own threading. A dowel screw functions like a dowel with threads but forms a more permanent bond between the joined pieces. They are commonly used for woodworking projects and can be threaded from end to end without a gap.
A machine screw is like a bolt and has a diameter of 0.75 inches or less. Due to their size restriction, established by the American Society of Mechanical Engineers (ASME), machine screws are smaller than other types of screws. When joining or connecting two pieces of metal, machine screws are inserted into threaded holes. The threads’ size and helical ridges remain the same from the top of the screw to the tip.
Self-drilling screws create internal threading when they are installed. They are fully threaded from the tip to the head, with harder and more rigid threads than the materials they are joining. Self-drilling screws have a variety of tips in unique shapes. Notched tips or drill bit tips can easily be installed and create their own space in the substrate.
Sheet metal screws are designed to join metal pieces and have a threaded shank that covers its entire length with a rounded or flat head. The tip of a sheet metal screw is sharp so that it can pierce a piece of a metal substrate. Sheet metal screws can be self-drilling and self-tapping. They are made from hardened metals capable of drilling into a metal surface.
Socket screws feature a smooth shank and have an Allen head fastened using an Allen wrench only. Socket screws are available in different head shapes like buttons, socket caps, and counter sunk.
A stud is like a screw but does not have a head. Studs are often used in places where a component is assembled or de-clamped. Studs come in the following types; plain, collared, square cross-section plain, hexagonal socket head studs, etc. They are used to join internally threaded holes together.
One of the most common automotive applications is the wheel stud. When pressed into a hole in a wheel assembly, wheel studs often have ribbed bodies that hold them in place.
A nut comes with an internal thread that helps it work together with a bolt of the same size. These types of threaded fasteners provide improved grip and increased torque to users. They come in several varieties and designs that help them fit into various bolt shapes.
The different nut types include the following:
Cap nuts are known as dome or acorn nuts and have the shape of a dome on the closed end to protect the bolt-nut assembly.
Castle nuts have notches at one of their ends. Their design allows the insertion of pins through their notches. They are best used where there are low torque requirements.
A flange nut is like a flange bolt and screws with a wide flange at one side of the nut to distribute pressure to the piece being secured.
The hex nut is one of the most common and easy to install. Hex nuts have an internal thread in them. These are the most common nuts and are used in various industries with various applications.
Lock nuts are used to lock the nut in place without clamping another object.
Nylon lock nuts have the same shape as a hex nut but have a nylon collar that locks into the bolt to prevent loosening.
Shear nuts have a hexagonal gripping point that snaps off during the maximum torque, leaving just the nut, which is difficult to remove.
Weld nuts help to fasten components in hard-to-reach areas. They require welding onto the part surface.
Wing nuts are used in applications where the nut needs to be removed frequently. These nuts have two external “wing-shaped faces,” allowing easy manual turning.
Washers are used along with nuts and bolts. They are placed under joints, nuts, and axle bearings. Washers alleviate friction. They also help to eliminate leakages and isolate different components. Washers help prevent the loosening of components due to vibration. The outer diameter is twice the inner, which is used to distribute the load of what is being fastened. Examples include:
Flat washers are the most common type used to distribute a load of bolts, screws, or nuts evenly. They prevent corrosion between a steel screw and an aluminum surface. Installers can place a nylon washer under a machine screw to reduce noise and abrasion and offer electrical insulation.
Sealing washers are used for plumbing and hydraulic projects.
Flat washers, also called Type A plain washers, are thin, flat, and general-purpose circular washers with centrally located holes. Standardized flat washers may be designed using imperial or metric dimensions.
Countersunk washers serve the same function as a flat washer but provide a bearing surface for flat head screws. An additional application is providing a sealing function for flat head screws. Countersunk washers, sometimes referred to as finishing washers, have a countersink that captures the head of the fastener. When secured, they provide a flush surface.
A fender washer is a flat washer with a larger outer diameter in proportion to its center hole. They are made from a thinner gauge metal than most flat washers, are designed to spread the load on thin sheet metal, and are often used in sheet metal, plumbing, and electrical work. The name is derived from their use in the automotive industry, where they are used to mount fenders.
Lock washers (electrical contact washers) are designed to prevent bolted joints from loosening using friction. Lock washers feature teeth-like serrations either internally or externally.
When the bolted joint is tightened, these teeth bite into the mating surface. External teeth lock washers have a cylindrical inner diameter with several teeth along the outside diameter aligned at an angle to the face of the washer. Internal teeth lock washers have a cylindrical outer diameter with several teeth along the inside diameter that is aligned at an angle to the face of the washer.
Sealing Washers—often rubber or neoprene washers—are placed on a fastener to prevent water from flowing through the fastener hole. When installed in a sealing application, the materials in sealing washers compress against either a flexible or an inflexible surface to form a permanent seal.
C-washers have a slot cut from the center to the perimeter. Typically, the slot is the same width as the “center hole,” allowing the washer to be removed, replaced, or inserted without completely removing the fastener.
Slotted “C” flat washers will enable you to assemble and disassemble bolted joints without separating bolts, nuts, and washer installation. The open slot allows the C-shaped washer to be slipped in and out.
Spring washers are locking washers used when there is a need to prevent a fastener from loosening due to vibration. They are also often called split lock or split ring washers. A spring washer has a split in the washer section that, when tightened, each side of the split bites into the nut and the mounting surface. This “bite” prevents anti-clockwise rotation from occurring under vibration.
Structural washers are thick, strong washers used in heavy-duty building construction for leveling and shimming applications. Structural washers are typically coated or galvanized for corrosion resistance for exterior building applications.
Torque washers are designed for use in a soft, penetrable material in which a bolt would not be able to stay fastened tightly inside. Torque washers have prongs that dig into the material, anchoring the bolt to combat loosening.
Rivets and riveting systems are categorized as permanent fasteners, which cannot be removed or reused once installed. Rivets are used in various industries to fulfill multiple applications but are commonly used to join metal sheets and plates. They come with a head at each end to support axial loads. Rivet guns are used to install rivets into components.
The common types of rivets are:
Solid rivets, also known as round rivets, are the most common type of rivets. They have a basic construction featuring a head and tail. They can be efficiently utilized using a hammer, rivet, or crimping tool. You should opt for solid rivets if you’re looking for an affordable and readily available type that offers high strength and reliability.
Tubular rivets are like solid rivets. However, tubular rivets come with a hollow end on their other side, unlike solid rivets. This unique design makes it possible to utilize little effort in fastening the rivets, resulting in an efficient installation process. Tubular rivets are used in brakes, lighting, HVAC ductwork, electronics, and mechanical products. However, tubular rivets can only be used when you have access to both sides of the parts to be assembled.
POP rivets are tubular rivets with a hat and a mandrel. The ability to set rivets without needing access at the back of the workpiece makes their use, in many instances, mandatory. There is no difference between pop rivets and blind rivets. These are different labels for the same item; a blind rivet means you do not need access to the other side of the material, or you can’t see the other side of the material.
Pop rivets consist of two parts. The first part is called the rivet body (aka, the shell or hat), and the second is called the mandrel (aka, the stem). When access to both component sides is limited, a hole is first drilled through the parts to be joined. A pop rivet is inserted through the drilled hole, and the rivet body is brought into contact with the parts. A pop rivet gun is placed on the rivet, pulling the mandrel into the rivet body, causing it to expand and grip the parts to be joined. Once seized, the mandrel snaps, permanently holding the rivet in place. This causes the rivets’ ends to expand, locking the parts together and generating a popping sound (which is why they are also called pop rivets).
These rivets offer easy installation and eliminate the possibility of under-torque or over-torque ordinary in conventional fasteners.
Drive rivets are similar to blind rivets: they feature a mandrel through their center. However, unlike blind rivets, drive rivets do not require any unique tool to draw the mandrel through the rivet. Instead, you only need a hammer and a backing block to draw the mandrel into the rivet body and lock parts to be assembled. Drive rivets are ideal for any application where the holes do not penetrate the entire panel, metal sheet, or block.
Split rivets, also referred to as bifurcated rivets, feature sharp ends split into two parts, allowing them to pierce materials. When installed in parts to be assembled, the split legs of the split rivets bend to hold the pieces together. They are ideal for joining soft materials like leather, wood, and plastic.
Flush rivets, also called countersunk rivets, are among the essential rivets used in applications that require excellent appearance and surface finish after assembly. This is because of their unique design, which features both countersunk heads and holes. Flush rivets’ countersunk heads and holes allow you to connect two parts such that the head of the rivet does not protrude above the surface of the metals.
As we can see fasteners come in many different forms, which all have a specific purpose or application in mind. Combined with the attributes of fasteners, such as type, materials, and coatings, there are hundreds (if not thousands) of combinations that may work best in your manufacturing process.
At Fastbolt, we are dedicated to ensuring that you are supplied with the right fasteners or hardware that you need. Our experienced team of global supply chain experts can help with any questions and specifications you need. Just reach out to us on our contact page to talk to a fastener supply specialist