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What is a Coil Spring?

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A coil spring is a mechanical component made from a tightly wound helical coil of metal that compresses or expands to absorb energy. Most springs that we’re used to from everyday life, such as springs in pens and mattresses, are coil springs.

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Coil springs are a broad category of metal part that are used in nearly every industry. They are commonly used in various industrial settings for shock absorption, load-bearing, and maintaining force in machinery. Coil springs can also be known as spring coils.

Coil springs play a critical role in automotive suspensions, industrial machinery, and even aerospace applications, providing stability and resilience in everything from common daily situations to demanding environments. From high-performance vehicles to precision medical devices, coil springs are essential to many industries.

How Does a Coil Spring Work?

A coiled spring operates by absorbing energy through compression or expansion. When force is applied, the coil compresses or stretches, storing energy in its metal structure, which is then released when the force is removed. Springs that compress fall into a broad category called compression springs, and have space between each coil so coils can be pushed toward each other. Springs that expand are known as extension springs, which are usually more tightly wound so individual coils can move away from one another when stretched. While compression and extension springs are the most common types of springs, there are many other types of coil springs, including torsion springs, which twist around an axis.

The simple – yet effective – mechanism of compression or expansion allows coil springs to act as energy dampers, which is essential in systems like the coil spring suspension system used in vehicles. By providing shock absorption, coil springs help reduce vibrations and improve stability across many applications, from industrial machinery to consumer products.

Examples of Coil Springs at Work

Coil springs serve essential functions in many applications, from managing weight loads to reducing mechanical wear. Here are some key examples of areas where coil springs are utilized:

• Automotive suspension systems – the suspension springs in passenger vehicles, heavy trucks, and other vehicles are compression coil springs (Looking for replacement car springs? Check out our selection here.)
• Industrial machinery for shock absorption – die springs, another type of compression coil spring, are frequently used in industrial machinery
• Aerospace applications for stabilizing loads – aerospace springs can do everything from help open doors or control rudders to absorbing shock and vibration
• Medical devices for precision control – medical springs are particularly important. Coil springs control the delivery of drugs in inhalers, support movement in medical equipment, and much more.

How Long Do Coil Springs Last?

The longevity of a coil spring largely depends on its use and the environment. In general, coil springs in standard automotive applications can last between 50,000 to 100,000 miles. However, exposure to extreme stress or corrosive elements may reduce their lifespan.

In other applications, coil spring lifespan will depend heavily on the type of spring (compression, extension, torsion, etc) as well as on the material, tolerances, and other technical specifications for the springs.

Coil Spring Types

Coil springs can be broken into various categories depending your use case. Different coil spring types could be based on how the spring works, such as compression, extension, or the twisting motion of a torsion spring. You can also categorize coil springs by rate, which is commonly used for automotive coil springs.

In terms of rate, there are two main types of coil springs: constant rate and variable rate. Constant rate coil springs, as the name implies, have a consistent spring rate throughout their compression. This means they exert a uniform resistance when force is applied, making them ideal for applications requiring stability, such as in automotive suspensions where consistent load distribution is necessary.

In contrast, variable rate coil springs, also known as variable pitch coil springs, provide different levels of resistance as they compress. These springs become stiffer as they are compressed, offering flexibility for applications that need additional resistance under high loads, like off-road vehicle suspensions or heavy machinery. This variation allows for better adaptability in applications subject to different load conditions.

What are Coil Springs Made of?

Coil springs can be made from a wide range of materials some of the most common being steel, music wire, and different grades of stainless steel. Automotive coil springs are typically made from high-strength steel, but coil springs may be made out of many different materials including, but not limited to:

• Copper
• Carbon steel
• Music wire
• Nickel
• Steel
• Stainless steel, such as medical-grade 316 stainless steel springs
• Titanium

Three main factors influence a coil spring's performance: the amount of coils, wire gauge, and material composition. These elements determine the spring’s durability, strength, and how it will respond to different stresses, shaping its suitability for specific tasks.

Amount of Coils

The number of coils in a spring directly affects its stiffness and flexibility. A coil spring with more coils generally has more flexibility and less stiffness, making it suitable for lighter loads and applications requiring higher elasticity. Conversely, fewer coils create a stiffer spring, ideal for heavy-duty tasks where greater force resistance is necessary.

Wire Gauge

The thickness, or gauge, of the wire used in a coil spring affects its resilience and ability to withstand stress. Thicker wire gauges result in stiffer, more durable springs suitable for heavier loads, whereas thinner gauges provide more flexibility and are typically used in lighter load applications.

Material Makeup

The material used for the coil spring, such as carbon steel, stainless steel, or alloy metals, influences its strength, resistance to corrosion, and heat tolerance. Carbon steel is commonly used for high-strength applications, while stainless steel offers better corrosion resistance, making it suitable for environments with moisture or chemical exposure.

Coil Spring Overview

Coil spring is a broad category of mechanical part that encompasses most common springs that consumers and businesses are familiar with. Some recognizable examples include the springs that retract the tips of pens, as well as car suspension springs.

Coil springs, however, are just one type of spring. Machined springs, flat springs, and other spring types are also available from major spring manufacturers like Components.