Fasteners are pieces of hardware that close or secure parts together without creating a permanent joint like welding or riveting. Ropes and hinges can technically fall under this definition but are not called fasteners due to their applications and flexible nature. Fasteners are specific items that form rigid connections.
Fasteners are typically made from steel, titanium, and aluminum. They often have coatings like black oxidizing, cadmium, phosphate, silver, and nickel to prevent corrosion and increase wear-time.
At Aerospace Aces, owned and operated by ASAP Semiconductor, we supply aircraft fasteners from some of the top manufacturers around the world. High-quality manufacturers include Arconic, Monogram, Beechcraft, and Textron.
Standards and Traceability
Fasteners are used across multiple industries. Many fasteners vary in quality, with high-risk environments requiring higher standards for composition, design, materials, and safety specifications. The aerospace, marine, and automotive industries all have higher standards for fasteners due to their operating environments.
Hardware components are commonly traded items. Because of this and their various uses, there are uniform standards. The American Society of Mechanical Engineers (ASME) has produced several standards that clarify definitions and types of fasteners, as well as the materials and dimensions that should be used. Fasteners used in military equipment must also meet standards applied to fasteners used in such applications.
Military standards also require traceability, an important resource for ensuring safety and conformity.
Types
Fastener categories include bolts, clamps, pins, pegs, nuts, screws, studs, ties, and washers.
Drive types include Phillips and Frearson, slotted, combination, socket, and star.
Washer types include flat, fender, split lock, internal tooth lock, square, and ogee.
Nut types include hex, nylon insert lock, jam, wing, cap, flange, tee, square, coupling, slotted, and pin lock.
Anchoring products include stud anchors, lag shields, drop-in anchors, concrete screws, conical anchors, and anchor bolts.
Aerospace Fasteners
While fasteners used in the aerospace industry look similar in appearance and function to those used in other industries, they differ significantly in material, quality, and weight. Aerospace fasteners have to operate in environments that bring a risk of corrosion, extreme stress and loads, high pressures, and exposure to very high and very low temperatures. This means that aerospace fasteners must be made from specific materials and be designed and manufactured to higher standards.
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Aluminum: Aluminum is a common choice for fasteners in the aerospace industry due to its light weight. However, aluminum requires extra treatment if it is to be used in spacecraft. Aluminum has to be cold-formed, is not optimal if expected temperatures exceed 350 degrees Fahrenheit and is vulnerable to stress-induced corrosion.
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Steel: The various types of steel are strong, but also heavy, which is a recurring problem for aircraft components. Stainless steel and alloys are the most frequently used types of steel used in the aerospace industry. CRES steel Series 300 is often used for screws and bolts and is resistant to corrosion but sensitive to high temperatures. Series 400 is resistant to heat, but vulnerable to rust. Alloy steels are durable, but also vulnerable to corrosion. There are treatments that can be used to increase corrosion and heat resistance, but these treatments can also cause steel to lose its resistance to tension corrosion.
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Superalloys: Superalloys are often used in aerospace because they are versatile, strong, and can withstand extreme temperatures. Superalloys include Inconel 718, H-11, Waspaloy, Hastelloy, K-Monel, and MP159. Choosing the right superalloy depends on the stresses the fastener will be exposed to.
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Titanium: Titanium is as strong as steel, and lighter as well, making it a popular choice for aerospace fasteners and assembly.
Automotive Fasteners
The automotive industry uses many different types of fasteners, but the most common are bolts, nuts, and studs. They vary by material minimum yield strength and minimum tensile strength and are ranked on a graded system set by the Society of Automotive Engineers (SAE).
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Automotive Bolts: Also referred to as threaded fasteners, these components are used in high tensile applications that need a rigid and strong attachment. Bolts are headed, with a threaded blunt end. Compared to other fasteners, bolts have a longer grip length, and a shorter portion for the attachment of a nut. Common bolts are hub bolts, wheel bolts, and U-bolts.
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Automotive Nuts: Automotive nuts are hex or square-shaped, with a threaded circle in their center. They are used to fasten and secure bolts, and their grade must match or be higher than the paired bolt. Automotive nuts are used in many common applications but can be used in more complex functions where a t-nut, collar nut, and locking nut may be used.
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Automotive Studs: Automotive studs are threaded on both ends and have an unthreaded middle section. They are secured to components using nut screws and are made from a variety of materials including bronze, aluminum, copper, and brass. Studs are commonly used in the build of an automotive engine, securing the cylinders and gasket head, or situations that need a higher stress tolerance than what a bolt can provide.
Automotive fasteners are graded by SAE (fractional) grades, and metric grades. Fasteners of SAE 2, 5, 8, and metric grades of 5.8, 8.8, 10.9, and 12.9 are used in the industry. Each is classified by proof loads, yield strength, and tensile strength. Grade 5 (metric 8.8) and Grade 8 (metric 10.9) fasteners are the most commonly used fasteners in automobiles.
Marine Fasteners
The greatest challenge for fasteners used in marine applications is the corrosive properties of saltwater. Coupled with the presence of wood materials, galvanic and crevice corrosion are also common issues. Marine fasteners are therefore sorted by their intended use and materials.
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Stainless steel: most marine fasteners use stainless steel in their construction. Stainless steel is resistant to corrosion and offers optimal strength and rigidity for marine applications. CRES Series Steel 18-8, 304, and 316 are used in the marine industry, with 316 offering the best corrosion resistance.
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Hot Dipped Galvanized Fasteners: Stainless steel is dipped in a layer of zinc, creating a bonded alloy. Fasteners that undergo the process have greater tensile strength and are more resistant to corrosion than regular untreated steel. Zinc plated steel is considered the best option for engine applications. Fasteners of this type are used in applications with higher loads, including the shaft coupler.
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Silicon Bronze: silicon bronze is made primarily from copper, with silicon and corrosion-resistant alloys like zinc. Silicon bronze fasteners are used in applications that frequently come in contact with water, applications beneath the waterline, and wooden vessel construction. Silicon bronze is extremely resistant to corrosion from liquids and operates well in the absence of oxygen. It is also less likely to galvanize other metals it is secured to.
