Fastener Design

Production Process
Fabricators create the threads on threaded fasteners in many different ways. To start, they typically inject mold plastic fasteners, and cast or heat metal ones from sheet metal. Fabricators create threads via thread rolling or thread cutting. Thread rolling a metal fastener involves cold forming the metal under pressure into the right profile. This process gives the metal better resistance to abrasion and a stronger thread. When manufacturers perform thread cutting, they simply cut the thread pattern into the blank metal.
Steel is a formable, strong, and durable iron alloy. Steel fasteners are popular for use with a wide variety of applications, depending on their carbon content.

Stainless steel is an extra durable alloy steel. It is popular choice for many industries, such as automotive engineering, because these stainless-steel fasteners are strong and resistant to corrosion.

Brass is a light duty alloy of copper and zinc. It is strong, corrosion resistant, and quite an attractive yellow color. Manufacturers usually use brass screws to secure decorative pieces, functional items they want to look nice, and for items to be used in or near seawater.

Bronze is another light duty copper alloy. This time, it is alloyed with zinc. Bronze alloys are ductile, lightweight, good conductors of heat and electricity, and corrosion resistant. Like brass, they have a nice color and sheen, though it can tarnish over time. Bronze fasteners can be used for applications very similar to brass.

Titanium fasteners are the number one choice for the aerospace industry because they are durable enough to be used as airplane construction fasteners. They are also extremely lightweight and strong.

Plastic fasteners are used for very light duty applications, like children’s toys, where strength is not a major concern.

Fastener Considerations and Customization

When designing or assigning fasteners for their customers, fastener manufacturers consider several important variables. These include the weight that the fastener will be expected to bear, the environmental conditions, and the space limitations.

These variables help manufacturers choose and customize details like the head type, the length, the fastener material, necessary coatings, screw grade strength, and decorative components. They will also decide on threads, or lack thereof, thread texture (coarse threads, smooth threads, etc.), and thread measurements.

These details are all important for different reasons. First, the head type makes a difference, as a wider head offers force on a greater surface area. Next, the correct length ensures that the fastener is flush with the surface. Third, because most outdoor applications require fasteners that will resist corrosion and ultraviolet deterioration, manufacturers must often apply protective coatings. Fourth, in machinery, manufacturers choose the strength grade that will keep the fastener from experiencing breakage or failure during operation. Next, when a fastener is used decoratively or fastens a decorative piece, manufacturers must make sure they choose a fastener that will not expose the head. Finally, threads largely dictate how the fastener will function.

Types of Fasteners

For the best organization, we can divide industrial fasteners into two overarching groups: threaded fasteners and non-threaded fasteners.

Threaded Fasteners

Threaded fasteners are those fasteners that feature spiral ridges, called threads, on their body. Threads help them stay secure.

Prominent examples of thread fasteners included nuts, bolts, screws, studs, clinching fasteners, hex bolts, self-tapping screws, cap screws, tap-end studs, double-end studs, and continuous-thread studs.

Nuts are metal blocks designed to work with bolts in order to create a strong attachment between the joining surfaces. To do so, they use internal threads that fit and hold onto the upper shaft of bolts.

Bolts (bolt stud fasteners) , the counterpart of nuts, feature an external, partially threaded shaft. Users push them through the workpiece and secure them on the other side with nuts. Together nuts and bolts are known as nut and bolt assemblies.

Screws are an extremely broad category of externally threaded fasteners. In general, they feature a spiral shaped thread shaft and a head. Since they feature a head, they do not need any other hardware to stay in place.

Studs are metal shafts or rods with threads on both sides.

Clinching fasteners, sometimes called clinch fasteners, self-clinching fasteners, or captive fasteners, are fasteners that when driven into ductile metal, deform the metal around the workpiece mounting hole. When they do so, the displaced metal cold flows into an annular recess located in the fastener pilot or shank. Clinching fasteners contrast with those fasteners that deform when they are installed.

Hex bolts are bolts that feature a hexagon shaped head. They are common for use in construction.

Self-tapping screws can tap their own hole as a user drives them into place. Self-tapping screws can be utilized on a variety of surfaces, including wood, metal, and bricks. Because these screws cannot drill through metal, a pilot hole must be bored before installation.

Cap screws are fully threaded fasteners designed to fasten machine parts.

Tap-end studs are studs that feature long threads on one end and short ends on the other. The long end is called a nut-end. Users can round or chamfer the long end, and they can screw the short end into tapped holes.

Double-end studs are those studs that feature chamfered points and threads of equal lengths on both ends. Most often, customers purchase this type of fastener for flange bolting.

Continuous thread studs are studs that have no break in their threading. Rather, they are threaded continuously from end to end. Customers also often use continuous thread studs for flange bolting, though to do so, they must also use two nuts.

Non-Threaded Fasteners

Non-threaded fasteners are those fasteners that do not feature threads. Without threads, they are easier to install and easier to remove. Also, they do not require accessories like screwdrivers.

Some of the most common non-threaded fastener varieties include pin fasteners, retaining rings, rivet fasteners, blind rivet fasteners, and dowel pins.

Pin fasteners are simply steel pins that are most often cylindrical. With the help of a clip on the end, they fasten machine parts together and/or keep them in alignment. These come in handy in assemblies where the fastener must be removed frequently, like a tractor wagon. It would be too inconvenient to tighten and loosen a threaded bolt every time. In contrast, users can install and remove a pin in seconds.

Retaining ring fasteners hold parts and assemblies in housings or onto shafts. They prevent the assemblies or two parts from sliding around or slipping. They can do this because, when installed, they are sealed into position in a groove. Some are also self-locking mechanisms. Customers purchase retaining rings for use on pulleys, door hinges, and electronics, as well as on furniture to form connections.

Rivet fasteners, or rivets, are mechanical fasteners made up of a head attached to a smooth cylindrical shaft. Users install it by placing it inside a drilled or punched hole. When they do this, the tail end of the shaft deforms, becoming about one and a half times wider. This helps the rivet stay in place permanently. Customers often purchase rivets along with pins for more lasting and tamper-proof holds on pulleys and hinges.

Blind fastener rivets hold two parts together at the head of a rivet. Sometimes called pop fastener rivets or blind rivet nuts, these fasteners consist of a tubular shaft and a mandrel running through the middle. Users install it by placing it in a drilled hole and then pulling on the mandrel with a rivet gun. As users pull in the mandrel, it will pop off or break, causing the rivet head, or blind end, to expand and hold the two parts together. Manufacturers do not recommend blind rivet fasteners for critical structural applications because the mandrel could fall out and because they are more susceptible to vibration and corrosion. When customers do purchase blind rivets, it is usually for use with parts that they can only reach from one side.

Dowel pins hold parts together evenly to ensure perfect alignment. These solid cylindrical rods are generally quite small and are so useful in applications like toy making and shelf supports. To accommodate these applications, they may be rolled, tapered, or grooved.

Snap fasteners are specialty fasteners designed for use on items like shirts, pants, and some bags. Sometimes called snaps, press studs, or poppers, they are made up of two metal or plastic interlocking discs. To fasten, users simply have to apply pressure and they will snap shut. Often, snap fasteners go in the place of buttons.

Self drilling screws are utilized in a wide range of fastening and fixing applications. They are also referred to as Tek screws. The name Tek screw was originally a brand name for a popular maker of these screws, but it has since become associated with this type of fastener. Self-drilling screws have a drill-shaped point and are often made of stainless steel. This point allows the screws to drill into materials without the need for pre-drilled pilot holes, making the fastening procedure more efficient.

Self-drilling screws come in a variety of sizes, lengths, and thicknesses, making them useful and adaptable. The length of self-drilling screws is measured to the drill point tip. The length of a screw is measured from the flat part of the head to the tip or blunt end. After installation, the length of a screw is measured from where the screw would sit flush against the mating surface.

When attaching wood to metal that is more than 1/2 inches thick, fasteners with wings are required. The wings will widen a clearance hole, preventing the threads from engaging too soon. If the threads engage too early, the secured material may be separated from the base material.

Threads are helical splines or splines that spiral along the shank of the fastener. Threads come in a variety of shapes and sizes, but two varieties are commonly used on fasteners.

Machine screw threads are meant to pair with prepared threads in nuts or tapped holes and are found on bolts, setscrews, and machine screws.

Spaced threads are used in coach screws, self-tapping screws, woodscrews, and Type 25 thread cutters. In most cases, a spaced thread is designed to form its thread in a pre-drilled hole.

Stainless steel self-drilling screws are robust and long-lasting, making them an excellent choice for screws. The most common type of stainless steel used for machine screws and nuts is 18-8 stainless steel (non-magnetic). 18-8 stainless steel Self- should only be used for drilling into soft materials like wood. Some fastener lines, particularly self-drilling screws, use 410 stainless steel (magnetic), which is a hardened type. The hardening process increases the strength and stability of the product, which is especially useful when it is installed in metal parts.

Self-drilling screws are suitable for more demanding applications and industries, particularly when compared to self-tapping screws.

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