Types of fasteners
Non-permanent Threaded Fasteners
A Non-Permanent Threaded Fastener is a mechanical device used to hold two or more objects together in a way that allows for their separation without causing damage to the fastener or the objects being joined. This category of fasteners typically involves threads—a helical structure used to convert between rotational and linear movement or force.
- Screws
- Nuts
- Bolts
- Washers
Screws
Screws are a common type of fastener. They are usually made of metal and have spiral-shaped raised stripes called threads that thread into objects to join parts together. Their design allows the force exerted by rotation to be converted into downward pressure, ensuring that they remain tightly anchored in the material.
Screws are designed with various heads, threads, and points, each serving a specific purpose. Here are some common types of screws based on their design:
Flat Head Screws
These are countersunk screws with a flat top. They are used when a smooth finish is required, allowing the screw to sit flush with the surface.
Pan Head Screws
These have a rounded top and a flat underside, which offers a low profile when installed. They are commonly used in cabinetry and metalwork.
Round Head Screws
With a dome-shaped head, these screws are not countersunk and are used where the screw head can protrude above the surface, such as in decorative hardware.
Hex Head Screws
Featuring a hexagonal head, these are driven with a wrench or socket and are often used in construction and machinery where a robust head is beneficial.
Phillips Head Screws
Characterized by a cross-shaped recess that accepts a Phillips screwdriver, these are widely used because the design allows more torque to be applied.
Torx Screws
Known for their star-shaped recess, Torx screws offer improved torque transfer over Phillips head screws and are increasingly popular in the automotive and electronics industries.
Set Screws
These are headless screws used to secure an object within or against another object, typically using an internal wrenching drive like an Allen or hex socket.
Nuts
Nuts are an essential counterpart to bolts and screws, providing the necessary tension and load distribution to create secure joints. There are many types of nuts, each specialized for different applications and environments:
Hex Nuts
The most common type, with a hexagonal shape, is typically used in conjunction with a bolt or screw to fasten together multiple parts.
Lock Nuts
Designed to resist loosening under vibration and torque. Varieties include nylon insert lock nuts (nylon nuts) and those with distorted threads like the all-metal lock nuts.
Flange Nuts
These nuts have an integrated washer-like flange at one end, which provides a larger surface area to prevent damage to the material being fastened.
Wing Nuts
Known for their “wings” which allow for manual turning and tightening, making them useful in applications where frequent adjustments are needed.
Coupling Nuts
Long, hex-shaped nuts are used to connect two pieces of threaded rod or other male threaded fasteners.
Square Nuts
With a four-sided, square shape offering a larger surface area against the part being fastened, these nuts are less likely to become rounded off with repeated use.
Bolts
Bolts are a type of fastener designed to secure materials together through pre-drilled holes, typically used in conjunction with nuts. They have a head on one end and threads on the other, allowing them to be tightened and released as needed, making them ideal for both temporary and permanent applications.
Hex Bolts
Characterized by a hexagonal head, these bolts are the most common type and are used in a variety of applications that require a strong fastening, often with a matching hex nut.
Carriage Bolts
Known for their smooth, rounded head and a square section underneath, which prevents the bolt from turning when the nut is tightened. They are typically used in wood connections.
Anchor Bolts
These are embedded in concrete or masonry to provide structural support and connection to external loads. They include designs like the J-bolt and L-bolt.
U-Bolts
As the name suggests, these bolts are shaped like the letter “U” with threaded ends on both sides. They are commonly used to support pipework or as part of a clamping system.
Eye Bolts
Featuring a loop on one end, eye bolts are used for attachment points in lifting operations or for securing cables and wires.
Tension Control Bolts (TC Bolts)
These bolts have a built-in indication for proper tensioning and are used in high-strength structural connections, often seen in steel frame construction.
Structural Bolts
Specially designed for steel-to-steel structural connections, they come in various types like A325 and A490 in the United States, with each specification designed for particular sizes and tension loads.
Flange Bolts
These have a flange under the head that acts like a washer to distribute the load. They are often used in vehicle frames and other applications where a smooth bolt head is required.
Lag Bolts (Lag Screws)
Large wood screws with a bolt head and are significantly stronger than ordinary screws. They are used to secure heavy materials like lumber or to affix items to wood.
Washers
Washers play a pivotal role in the integrity of fastening systems by evenly distributing the load of a bolt or screw over a larger area.
Flat Washers
The most basic type of washers is used to disperse the pressure of bolts or screw heads to protect the assembly surface from damage.
Spring Washers
Including wave washers and lock washers, used to prevent bolts or nuts from loosening due to vibration.
Lock Washers
Designed to prevent bolts or nuts from loosening, these washers bite into the material to resist rotation when tightening force is applied.
Structural Washers
Thicker washers, often used in the building and construction industry, to withstand higher loads.
Insulating Washers
Used in electrical applications to prevent the transfer of electrical current through bolts, usually made of non-conductive materials.
Permanent Fasteners
Permanent Fasteners are fastening devices intended to create a lasting joint between two or more objects, where the connection is not meant to be readily disassembled. They typically require destructive methods for removal, such as drilling or grinding, including fasteners like welded joints, rivets, and certain adhesives.
Nails
Nails constitute the most traditional form of permanent fasteners, forged from a long history of carpentry and construction. They are designed to be driven into materials like wood or drywall, providing a quick and efficient method of joining pieces with enduring hold.
Nail Type | Description |
Common Nails | Thick and sturdy with a wide head. |
Finishing Nails | Smaller head for a discreet look. |
Brad Nails | Very small head, often used with a nail gun. |
Roofing Nails | Short with a broad head to hold materials. |
Masonry Nails | Hardened steel for penetrating stone and concrete. |
Box Nails | Thinner than common nails to reduce splitting. |
Duplex Nails | Double head for easy removal. |
Rivets
Rivets are mechanical fasteners that are particularly useful for joining metal sheets and structural components where access from only one side is possible. They provide a permanent, tamper-proof bonding and are used in a wide range of heavy-duty applications.
Anchors
Anchors play a foundational role in construction, providing secure fixing points in a variety of base materials, from concrete and brick to drywall and stone. They are specifically designed to anchor fixtures into materials that might not support weight or tension using screws or nails alone.
Inserts
Inserts are integral components used to enhance thread performance in materials that are otherwise unsuitable for threading, such as soft metals, plastics, and composites. They provide durable, wear-resistant threads in materials that would quickly strip under the stress of repeated use.
Fasteners: How it used
Fasteners play a pivotal role in countless applications that are essential to our daily lives.
Fasteners play a pivotal role in countless applications that are essential to our daily lives. Their omnipresence, though often unnoticed, is critical to the functionality of various devices, structures, and machinery. Here are some key applications where fasteners are not just important, but indispensable:
Automotive Industry
From the assembly of engine components with bolts and screws to the use of washers to ensure even pressure distribution and prevent leaks, fasteners are integral to building reliable and safe vehicles. Nuts and bolts must withstand high temperatures and vibrations, while inserts are often used to reinforce threading in materials that undergo regular stress.
Construction and Infrastructure
In the world of construction, bolts, and anchors secure beams and girders, while nails and screws are fundamental for woodworking and finishing details. Even in concrete structures, fasteners such as anchors and inserts are employed to affix external elements securely.
Electronics and Gadgets
The miniaturization of devices requires tiny fasteners to assemble components tightly and accurately. These include micro screws and inserts that must be precision-engineered to fit and hold together the compact and delicate parts of smartphones, laptops, and other electronic devices.
Aerospace and Defense
The demand for durability and resistance to extreme conditions makes fasteners in this sector highly specialized. Aircraft and military equipment rely on rivets for aerodynamic integrity and bolts made of advanced materials that can endure the rigors of high-speed travel and harsh environments.
Furniture and Home Appliances
Fasteners such as screws, bolts, and nuts are fundamental in assembling furniture, securing cabinets, and affixing appliances to walls or countertops. Even the jam nut, a less celebrated component, proves essential in preventing loosening from frequent use or heavy loads.
Medical Devices
Precision fasteners, including specialized screws and inserts, are used in medical devices where non-reactive and biocompatible materials are critical. They ensure the devices function reliably under strict hygiene and performance standards.
Common Materials Used for Fasteners
Steel
Steel reigns supreme as the primary material for fasteners, prized for its high tensile strength and cost-efficiency. Ideal for heavy-load applications like construction, carbon steel is common, though prone to rust, which limits its use in corrosive environments. When it comes to specific standards and specifications, such as fastener size, strength, corrosion resistance, etc., a series of standards and specifications are referenced. For example, ASTM A325, ASTM F593, and the automotive industry standard SAE J429.
Stainless Steel
Stainless steel fasteners, known for their rust resistance and durability, are indispensable in settings exposed to moisture or chemicals. While more costly, they offer longevity that often offsets the upfront investment, making them a wise choice for marine and industrial uses.
Brass, Aluminum, and Plastics
For specialty needs, brass is chosen for its low friction; aluminum for its lightweight and non-magnetic nature; and plastics for their corrosion resistance and non-conductivity, catering to specific demands in electrical, aerospace, and decorative applications.
Conclusion
In modern engineering, the selection of appropriate fasteners is crucial for ensuring structural integrity and longevity. The myriad types of fasteners, from the steadfast jam nut to a spectrum of screws, bolts, and nuts, demand careful selection to match the unique specifications of each manufactured part.
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