Fasteners

Fasteners are devices that mechanically join or affix two or more objects together. They create non-permanent joints, which means the objects can be disassembled without damaging the joining components. Used across industries, from automotive to aerospace, construction to electronics, fasteners are ubiquitous in our everyday life.

Types of Fasteners

Fasteners come in various forms, each designed for specific uses and materials. Here are some of the most common types:

• Screws: These are characterized by their helical ridge, known as a male thread. Screws are typically used to hold objects together and to position objects.
• Nuts: These fasteners have a threaded hole. They are used in conjunction with a mating bolt to fasten multiple parts together.
• Bolts: Like screws, bolts also have a helical ridge, but they require a nut or equivalent female thread to function.
• Washers: These are thin plates with a hole that are typically used to distribute the load of a threaded fastener, such as a bolt or nut.
• Rivets: These are permanent mechanical fasteners. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end.

Materials and Coatings

Fasteners are made from a wide variety of materials, including steel, stainless steel, brass, nylon, and plastic. Each material has unique characteristics, making it suitable for certain applications.

Steel fasteners are common because they are strong and affordable. They may be alloyed with other elements to improve their properties, such as increased corrosion resistance or hardness.

Stainless steel fasteners are used when resistance to corrosion is vital. They are ideal for outdoor applications and in environments where they may be exposed to moisture.

Brass fasteners are corrosion-resistant and electricity conductive. They are often used in electrical applications.

Nylon and plastic fasteners are lightweight and resistant to corrosion and electricity, making them ideal for certain applications.

Fasteners often have coatings or platings, such as zinc, cadmium, or nickel, to enhance their corrosion resistance. A newer development is the application of molecular coatings that can provide superior resistance to corrosion and reduce friction during assembly.

Design Considerations

When choosing a fastener, several factors need to be considered:

• Material Compatibility: The fastener material should be compatible with the materials being joined to prevent galvanic corrosion.
• Load Requirements: Fasteners must be strong enough to handle the load placed on them. Shear strength (load across the axis) and tensile strength (pulling force) are important considerations.
• Environment: Fasteners used in harsh environments, like saltwater or chemicals, need to be corrosion resistant.
• Cost: While critical, cost needs to be balanced against the fastener's performance requirements.
• Accessibility for Assembly and Maintenance: Fasteners should be chosen based on whether the assembly is temporary or permanent and how often maintenance will be required.

Manufacturing Techniques

Fasteners are manufactured using several techniques, including threading, hot forging, cold forming, and turning.

Threading is a process used to create screw threads. This can be done by cutting or rolling. Rolling threads is a process that deforms the material to create the thread profile, which can increase the fastener's strength.

Hot forging and cold forming are processes used to shape metal using localized compressive forces. Hot forging is performed when the metal is hot, while cold forming is done at room temperature.

Turning is a machining process in which a cutting tool describes a helix toolpath by moving linearly while the workpiece rotates to create cylindrical parts, including fasteners.

Importance and Applications

Fasteners are unsung heroes in the world of mechanical design and assembly. They allow for the assembly of complex machines and structures from smaller, manufactured components, which can then be disassembled for maintenance or repair. Fasteners are used in virtually every industry, from automotive, aerospace, and marine applications to electronics, medical devices, and construction.

Beyond their practical applications, fasteners also have societal significance. They have enabled the creation of everything from cars and planes to buildings and bridges, facilitating the growth of our modern infrastructure.

In conclusion, while fasteners may seem simple or mundane, they are an essential component of modern design and manufacturing. Their selection requires careful consideration of materials, loads, and environmental factors, and their manufacture involves complex processes. As our technology evolves and our ambitions reach further, we will continue to rely on these small but mighty devices to hold our world together.