Types, Uses, and Designs of Coil Springs

Coil Springs: Types, Uses, and Designs

Introduction

This article takes an in depth look at coil springs and their materials.

You will learn more about topics such as:

What is a Coil Spring?
How Coil Springs are Made
Metals Used to Make Coil Springs
Types of Coil Springs
And Much More ��

Chapter One �� What is a Coil Spring?

A coil spring is a helical mechanical element made by winding metal into a spiral form. It functions to store potential energy, which it then uses to mitigate shock. These springs are manufactured by twisting metal wire into a continuous helix, transforming the wire into an energy-storing component.

Available in various sizes, coil springs are engineered to reduce impact and stress on different surfaces. They achieve this by providing flexibility that allows them to deform under external stress and then bounce back to their original shape once the stress is lifted. During compression, the spring holds energy and releases it when returning to its initial form. The energy stored is proportional to the force applied.

When subjected to weight, coil springs compress, storing mechanical energy by reducing in size. After the weight is lifted, the spring expands, releasing the stored energy as it returns to its original state.

Coil springs can be classified into three main categories: compression, extension, and torsion, each serving a unique function. Among these, compression springs are the most prevalent. They are typically produced by hot or cold winding of spring steel and are engineered to absorb force and resist compression.

Coil springs may be prone to corrosion and environmental degradation, potentially causing early failure. To improve endurance, they are frequently coated with substances such as powder, epoxy, or polyester. Additionally, some springs are electroplated with zinc or nickel to enhance their protective capabilities.

Chapter Two �� How Coil Springs are Made?

Coil springs are essential elastic mechanical components engineered to absorb, store, and release energy in a wide range of industrial, automotive, and consumer applications. As fundamental elements in suspension systems, mechanical devices, and precision instruments, coil springs play a pivotal role in maintaining force, shock absorption, and mechanical efficiency. Coil springs can be fabricated from various spring steel alloys, with material selection tailored to the requirements of the load, environment, and application. There are two main types based on coil spacing: close wound coil springs, where the coils are tightly compressed and touch one another, and open wound coil springs, in which spaced coils provide variable deflection and elasticity.

The manufacturing approach for coil springs depends on factors such as production volume, required tolerances, and application standards. For limited or custom runs, manufacturers often use manual or lathe-based methods. However, for mass production of high-performance coil springs, automated spring coiling machines or advanced computer numerical control (CNC) systems are employed to achieve consistent precision, greater efficiency, and tight quality control.

The Manufacturing of Coil Springs

Coil Spring Materials

Coil springs are typically constructed from an array of high-tensile and durable metals, each best suited for specific mechanical properties and environments. Common coil spring materials include high carbon steel (such as ASTM A228 music wire), medium carbon steel, chromium vanadium steel, chromium silicon steel, as well as corrosion-resistant stainless steel grades, copper alloys, and nickel-based alloys. Stainless steel coil springs are frequently used when high resistance to oxidation or harsh environments is required, such as in marine or food processing industries. The selection of spring steel or other alloys depends on factors such as fatigue strength, load capacity, resistance to wear, and environmental considerations.

Raw materials for manufacturing coil springs are often provided as bars or rods, which are drawn down into wire of the appropriate diameter. Wire diameter is a critical factor influencing the spring's final physical properties, including its spring constant (rate), load-bearing capacity, and durability. Material quality certifications (such as ISO or ASTM standards) and traceability are especially important for critical engineering applications and OEM (Original Equipment Manufacturer) contracts.

Coil Spring Manufacturing Processes

Cold Winding Process

Heat Treatment �� The heat treatment of spring wire precedes cold winding and is vital for optimizing wire strength, ductility, and resistance to mechanical fatigue. Cold winding is the preferred process for manufacturing coil springs with wire diameters up to 0.75 inches (18 mm), enabling the production of compression springs and extension springs with precise tolerances and repeatability.

Mandrel �� The mandrel coiling process can be performed manually—ideal for prototyping and small batch runs—or using semi-automated winding machines. During winding, the wire is tightly wrapped around a mandrel, guided to ensure the correct pitch and coil alignment. This process determines the spring’s free length, inner and outer diameters, and the number of active coils, key variables in the spring’s load and deflection characteristics.

Computer Numerical Control (CNC) �� CNC spring manufacturing represents the pinnacle of automation for coil spring fabrication. CNC machines integrate computer programming and servo-driven actuators, providing unparalleled control of wire feeding, winding, shaping, and cutting. This enables rapid production and high consistency essential for demanding sectors such as aerospace, heavy trucks, and industrial machinery. CNC coiling can handle different wire sizes and complex spring geometries—including barrel, conical, and variable-rate springs—ensuring repeatable precision in custom spring manufacturing projects.

Feed rollers pull the spring wire from the spool and supply it uniformly into the forming area.
Wire guides keep the wire on the correct axis and orientation during the coiling process, minimizing deviations.
Block guides ensure the wire is channeled precisely to the coiling point, maintaining spring dimensions and pitch consistency.
The arbor or coiling mandrel forms the central support for the wire as it is shaped into the coil form.
The pitch tool is controlled via CNC parameters, determining the spacing and angle of each coil turn to match custom spring requirements.
The coiling point, engineered for specific deflection, bends the wire to the programmed spring configuration.
Cutters separate the finished coil spring from the feed at precise intervals, optimizing production efficiency and minimizing scrap.

The following diagram details these CNC spring manufacturing components and workflow.

Hot Winding

Wire �� The hot winding process is recommended for coil springs made from thick wire, usually from 3 inches (75 mm) to 6 inches (150 mm) in diameter, as found in heavy-duty suspension springs, mining equipment, and railroad applications. Coil spring wire is heated in a controlled furnace to approximately 1700°F, greatly increasing its malleability and permitting tight radius winding without cracking or surface defects.

Mandrel �� In automated hot coiling, the red-hot wire is wound around a precision mandrel, while CNC robotics ensure exact pitch and coil geometry, even under the stresses of high-temperature deformation. This results in heavy coil springs that meet strict automotive, industrial, or construction-grade performance standards.

Heated Metal Being Coiled Around the Mandrel to Make a Coiled Spring

Cooling �� Rapidly cooling, or quenching, is a critical post-hot-winding step to harden the newly formed coil and lock in the desired microstructure. Oil quenching is widely used in the spring industry for its speed and ability to minimize metallurgical gradients, which can otherwise cause spring failures due to cracking or embrittlement. Consistent cooling is monitored to establish the final spring hardness and ensure compliance with ISO or SAE spring manufacturing standards.

Throughout quenching, significant changes occur in the steel’s crystalline lattice, resulting in enhanced strength and increased spring life cycles. Using high-quality quenching oils or advanced cooling systems directly impacts coil spring reliability in demanding applications such as vehicle suspension, agricultural machinery, and critical industrial equipment.

Placing a Hot Coiled Spring in a Quenching or Cooling Bath

Stress Relief

The mechanical coil forming process subjects spring wire to high levels of internal strain, resulting in residual stresses that can compromise coil performance, reduce fatigue resistance, or cause premature failure under load. Stress relief is an essential step in the coil spring manufacturing workflow to release these built-in stresses, enhance reliability, and extend service life.

Typically, springs are heated in a controlled oven to temperatures below their recrystallization point, holding them there long enough for molecular rearrangement without altering the spring’s shape. Gradual cooling follows to preserve the optimal physical and metallurgical properties. The exact settings vary by material: for example, chrome silicon and chrome vanadium may undergo stress relief at 700°F��800°F (371°C��426°C), while 17-7 stainless steel requires higher temperatures. Proper stress relief is especially crucial for high-load compression springs and precision extension springs used in automotive, aerospace, and industrial assemblies.

Finishing a Coiled Spring

The finishing phase involves surface treatments and machining operations that prepare coil springs for end use and optimize their longevity, corrosion resistance, and precision tolerances.

Grinding �� End grinding ensures that compression springs or heavy load coil springs have flat, parallel surfaces, allowing stable seating and uniform force distribution in mechanical assemblies. Precise grinding is essential for coil springs in automotive suspensions, valve actuators, and shock absorbers. Lubrication and coolant systems are utilized to maintain dimensional accuracy and prevent thermal warping during high-speed grinding operations.

Well-executed end grinding improves spring fit and functionality, preventing instability and ensuring maximum force transfer. Many OEMs and industrial buyers specify ground ends as a quality requirement for critical spring applications.

Shot Peening �� Shot peening is a high-impact finishing treatment in which spherical media (metal, glass, or ceramic) bombard the coil spring’s surface. This process introduces compressive stresses that greatly improve fatigue strength, resistance to crack propagation, and overall spring longevity—crucial in performance-critical industries such as automotive shock absorbers, industrial automation, and high-cycle machinery.

Set Pitch and Length �� Custom spring manufacturers often compress and test coil springs to their working length and required pitch, repeating this process to achieve the precise specification demanded by OEM and industrial customers. The spring’s pitch, length, and number of active coils are critical for ensuring engineered load ratings and deflection tolerances. Sophisticated measuring systems and spring testing machines are frequently used to guarantee conformity with design data sheets and application requirements.

Debate exists within the spring manufacturing industry about the most accurate way to characterize spring geometry, with some engineers prioritizing the number of active coils over pitch as a key determinant of spring function in complex assemblies.

Applying Coatings �� Applying protective coatings is vital to preventing corrosion, abrasion, and surface fatigue in coil springs, extending their operational lifespan even under exposure to water, chemicals, or salt. The most common coil spring coatings and finishes include:

Zinc coatings: Offer robust corrosion resistance and are ideal for springs used outdoors or in high-moisture environments, as they prevent rust and extend operational life. Zinc coatings are typically applied via mechanical plating, electroplating, or hot-dip methods, each tailored to the coil spring size and use case.
Electroplating: Provides cost-effective and uniform metal deposition with options such as chromium, nickel, tin, or zinc. Tin and nickel finishes are preferred where electrical conductivity is essential—common in electrical contacts and high-frequency electronics.
Powder coatings: Deliver excellent chemical and abrasion resistance and enhance the aesthetic appeal of large industrial coil springs, machinery parts, or automotive coil springs. Available in a wide range of colors and thicknesses to meet customer branding requirements or regulatory compliance.
Pre-plated wire: Used directly in high-volume spring manufacturing, ensuring that every part of the spring, including interior surfaces, receives maximum corrosion protection. Galvanized wire is the industry standard for durable, rust-resistant coil springs in demanding or outdoor uses.
Plastic coating: Adds flexibility and resistance to chemical attack, but may be unsuitable for high-cycle or high-load springs due to wear issues associated with repeated compression.

Types of Coil Spring Ends

The design of coil spring ends is a critical consideration in spring engineering, as the shape and finish of the spring ends directly impact fit, seating, and performance in the final assembly. Selecting the appropriate end type for a compression or extension spring ensures a secure interface, proper load transfer, and long-term durability. The four most common types are:

Closed End

The closed end coil spring is the industry standard for stability and even load distribution. The end coil is wound so it sits flat against the adjacent coil, preventing rocking or tilting. Closed end designs are common in automotive coil springs and industrial hardware where precise upright positioning is crucial.

Square End

Square end coil springs, a subtype of closed ends, have their terminal coil ground perpendicular to the spring axis, forming a true 90-degree flat interface for maximum stability in perpendicular mounting scenarios. These spring ends are commonly specified for heavy-load or high-precision engineering contexts where maximum deflection and force transfer are required.

Open End

Open end coil springs retain their natural pitch to the very tip, forming a “tangential�� end. Frequently deployed in situations where the spring is seated in a recessed cup or groove, open end designs are popular in both automotive and mechanical equipment—especially where custom mounting and cost control are important. These springs must be supported by a compatible spring seat to ensure correct operation.

Pigtail Coil Spring

Pigtail coil springs, marked by a terminal coil with a smaller diameter, are engineered for attachment via screws or bolts—common in certain automotive suspension spring designs and industrial machine components. This specialized end allows for direct mechanical fastening, simplifying installation in complex assemblies.

How to Select the Right Coil Spring? When sourcing or specifying coil springs, consider key factors such as load capacity, spring rate, operating environment, fatigue life, installation constraints, and finishing requirements. Collaborate with reputable spring manufacturers who offer engineering support, material traceability, quality testing (including fatigue and load testing), and advanced manufacturing capabilities (manual, CNC, and custom solutions) to achieve the optimal balance of performance, price, and durability for your application.

Whether you are specifying automotive coil springs, industrial compression springs, or custom extension springs, partnering with knowledgeable spring suppliers ensures access to technical consultation, certified materials, and tailored design options that meet regulatory and performance standards.

Leading Manufacturers and Suppliers

Chapter Three �� What metals are used to make coil springs?

The initial step in coil spring manufacturing is selecting the appropriate metal for fabrication. A key factor in this selection is the tensile strength of the metal, which must meet the application's requirements. Most springs are made from steel alloys due to their availability and cost-effectiveness, though copper and nickel alloys are used for certain specialized applications.

The chosen metal must be capable of holding and releasing mechanical energy over an extended period without failure. High-quality coil springs are characterized by their ability to exert force between surfaces and to effectively absorb shock and stress.

Coil Spring Metals

High Carbon Steel

High carbon steel is widely used for manufacturing coil springs due to its strength, durability, and cost-effectiveness. This steel is available in 1045 and 1095 alloys and contains 1% carbon along with 0.9% manganese. Its very fine pearlite layer structure contributes to its hardness and brittleness, making it less ductile.

Music Wire �� Also known as piano wire, music wire is regarded as the toughest material for coil springs. It is a high carbon spring steel characterized by its uniformity, high tensile strength, and ability to endure stress from repeated loadings. Music wire offers excellent temperature resistance and is commonly used in environments with extremely high temperatures, such as in foundries and refractories.

Chromium Vanadium Steel

Chromium vanadium steel is known for its remarkable strength and flexibility. When utilized for coil springs, its medium carbon content imparts toughness and wear resistance. The inclusion of vanadium enhances its machinability, reducing the risk of breakage during shaping. Chromium vanadium steel is heat-treated during processing to improve its wear and fatigue resistance, making it suitable for high-stress environments with moderately elevated temperatures.

Chromium Silicon Steel

Chromium silicon steel is recognized for its exceptional hardness and capacity to endure high stress. Its durability and heat resistance make it suitable for applications at temperatures above 275°F. Originally developed for coil springs in anti-aircraft weapons, chromium silicon steel is designed to handle significant shock loads.

Stainless Steel

When discussing stainless steel, it's essential to specify the grade, as each has distinct properties tailored for particular applications.

Stainless Steel 302 is the most widely used stainless steel for coil springs. It is particularly effective in environments exposed to moisture or corrosive elements. Stainless Steel 302 can withstand high temperatures up to 550°F or 228°C. Among the stainless steel grades, it is the softest and most flexible while still maintaining high tensile strength.

Stainless Steel 316 is one of the cleanest stainless steels and has all of the other properties of resistance to moisture and can resist the effects of high temperatures. Although it has positive qualities, it is the weakest of the three types of wire used to produce coil springs.

Stainless Steel 17-7 offers excellent resistance to moisture and corrosion, and it is stronger and harder compared to 302 and 316 grades. Its increased hardness allows for the production of coil springs with enhanced force and stiffness. Stainless Steel 17-7 can withstand temperatures up to 650°F or 343°C.

Various Types of Stainless Steel Coil Springs

Silicon Manganese Steel

Silicon manganese steel enhances the steel's hardness, manages its decomposition during tempering, and strengthens its ferrite structure. Manganese further increases the steel's hardness and minimizes decarburization. Coil springs made from silicon manganese steel are hot-formed at 900°C, achieving a hardness of 225 BHN. These springs are commonly used in torsion bars, railway cars, automobile leaf springs, and stabilizers.

Copper Based Spring Alloys

Copper-based spring alloys are valued for their excellent electrical conductivity and high resistance to corrosion. However, their additional beneficial properties make them more costly. These alloys are commonly used in electrical components and in environments with extremely low temperatures.

Beryllium Copper stands out for its electrical conductivity, corrosion resistance, and superior mechanical strength, offering higher tensile strength and good fatigue resistance compared to other copper alloys. It maintains its ductility even under cryogenic conditions. The non-magnetic nature of beryllium copper makes it particularly suitable for medical applications, such as MRI machines, and for industrial uses like directional drilling equipment.

Phosphorus Bronze is an alloy of copper, tin, and phosphorus that offers superior corrosion resistance and strength compared to other copper alloys, thanks to the addition of tin. The phosphorus enhances wear resistance and increases the stiffness of coil springs made from this material. Phosphorus bronze coil springs exhibit excellent strength, good fatigue resistance, and machinability. They are commonly used in marine fuel pumps, oil rigs, and oil pipeline valves.

Nickel Based Spring Alloys

Nickel-based alloys are favored for coil spring production due to nickel's exceptional corrosion resistance and its capacity to endure both extremely high and low temperatures. These alloys are non-magnetic, making them suitable for use in gyroscopes, chronometers, and various indicator instruments. Additionally, they resist the effects of electrical currents and are poor electrical conductors. Nickel-based spring alloys typically have a Rockwell Hardness ranging from C35 to C48.

Below are some common nickel-based spring alloys:

Inconel X750 is a nickel-chromium alloy known for its high strength at temperatures up to 1300°F (740°C) and its oxidation resistance at temperatures up to 1800°F (982°C). It also exhibits excellent resistance to relaxation.

Inconel 600 is a nickel-chromium-iron alloy known for its exceptional resistance to corrosion and oxidation. It maintains excellent strength at high temperatures and is particularly resistant to chloride stress cracking due to its high nickel content. Inconel 600 also withstands attacks from both inorganic and organic chemicals and performs effectively at temperatures as low as ��300°F. This alloy is used in applications requiring a tensile strength of 220 Ksi, and the coil springs made from Inconel 600 are typically cold worked.

Inconel 625 is an alloy composed of nickel, chromium, molybdenum, and niobium, which impart exceptional corrosion and oxidation resistance, along with high strength at elevated temperatures. The strength of Inconel 625 is largely attributed to its molybdenum and niobium content. Similar to Inconel 600, it also resists chlorine stress corrosion cracking and pitting, making it suitable for marine and seawater applications.

Inconel 718 is a high-strength, age-hardened alloy made from nickel, chromium, niobium, and molybdenum, known for its excellent corrosion resistance. It performs well in extreme temperature conditions, both high and low. Inconel 718 is particularly well-suited for spring manufacturing due to its superior fatigue, creep, and rupture strength, making it ideal for various industrial applications and operations.

The metals mentioned above represent just a selection of materials used in coil spring production. Researchers and engineers are continually exploring new materials, such as aluminum, for potential use in coil springs.

Chapter Four �� What are the different types of coil springs?

Springs are classified into coil and non-coil types based on their design. Coil springs have a helical shape and are made from a single metal strand wound into a coil. The typical manufacturing process involves wrapping or winding the spring material around an arbor and coiling point.

Different types of coil springs have distinct characteristics that set them apart. Generally, coil springs are engineered to withstand various types of stress, such as compression or extension.

Coil Spring Types

Volute Spring

Volute springs are created from flat material coiled around an arbor to form a spiral scroll shape, known as a volute. These springs often resemble a tube with a smaller end, and some designs feature small ends at both extremities. After coiling, the material sheets are heated, which affects the spring's gap, shape, dimensions, and load characteristics. During compression, the overlapping flat sheets guide each other radially, enhancing the stability of the volute spring.

Arc Coil Springs

Arc coil springs, or bow springs, feature a curved shape resembling the arch of a bow. Unlike traditional springs that run straight from end to end, these springs have a central curve. Initially designed for use in dual mass flywheels within drive trains, arc coil springs apply force from both ends to bring objects closer together.

Variable Coil Springs

Variable coil springs feature varying distances between their turns, which affects how the spring compresses at different points. As the spring is compressed, the energy required changes with each turn, often following an exponential curve. This design enhances performance in several areas, including easier unlocking, better recoil energy storage, improved dampening, and more effective feeding, breaching, and lockup.

Torsion Coil Springs

Torsion coil springs are a flat spiral coil that is used to apply torque or store rotational energy. They store and release rotational energy via torque, which causes the spring to rotate on its axis to apply or resist a load. Torsion springs are attached to components that will rotate around their axis. In most cases, they are very tightly wound but also have versions that have pitch to reduce friction between the coils.

Torsion springs, like many other springs, can be oriented at various angles, either horizontally or vertically, and can rotate along or against their axis. When a torsion spring rotates, its coil tightens to either store or release energy. They are commonly used in applications such as mouse traps and self-closing screen doors.

Compression Springs

Compression coil springs are designed with a helical shape to resist forces applied along their axis. They are highly versatile and come in various sizes, ranging from those used in retractable pens to those found in automobile suspension systems. Compression springs come in different forms, including helical, conical, volute, barrel, and hourglass types.

Straight Coil compression springs feature coils that maintain a consistent diameter throughout their length. This type is the most commonly used compression spring.

Hourglass compression springs feature a tapered middle that narrows to a smaller diameter compared to the rest of the coils. This design ensures that the spring remains centered within a larger diameter hole. Hourglass springs combine some benefits of conical springs while offering symmetrical characteristics.

Barrel compression springs feature smaller diameters at the ends and a larger diameter in the middle. This design addresses a common issue with standard compression springs, which can buckle or bow under pressure. The barrel shape enhances flexibility, allows the spring to fit various designs, and distributes pressure more evenly due to its wider middle section, resulting in improved stability.

Extension Springs

Extension springs are like compression springs but are tightly wound and loaded with tension. They have hooks or loops at either end to apply pull force. Extension springs are attached at both ends to components. When the components move apart, the extension spring attempts to bring them back together. The initial tension in the spring determines how tightly coiled it is and can be changed to meet the needs of an application. The tight winding of extension springs is designed to oppose extension. In essence, they provide return force for components that have extended to the actuated position.

Chapter Five �� What are the uses of coil springs?

Coil springs are extensively utilized in a vast range of components, machines, devices, instruments, and vehicles. They play a crucial role in medical equipment, automobiles, heavy lifting machinery, and small delicate tools. Their capacity to store and release energy is essential for supporting and ensuring the efficient operation of these applications.

Coil Spring Uses

Automobile Uses

In trucks and cars, coil springs are a vital component of the suspension system, working in conjunction with struts and shocks. They absorb road impacts, support the vehicle’s weight, ensure a smooth ride, and maintain wheel contact with the road. In smaller applications, coil springs hold the hood open and regulate engine valve movement. Additionally, they contribute to the comfort of car seats.

Uses in Doors

Coil springs are extensively used in doors to facilitate opening and closing mechanisms. In garage doors, they are crucial for bearing the door's weight and keeping it in place until it is manually moved or closed. The design of coil springs for doors is tailored to the weight and size of the door to ensure reliability and prevent failure. For automatic doors, coil springs apply resistance to keep the doors closed but release their tension when the opening sensor is triggered.

Springs in Construction

Coil springs play a crucial role in construction projects, from anchoring new constructions to reinforcing existing foundations. They provide essential support for sidewalks, managing movement and motion. Additionally, coil springs are integral to safety release valves, facilitating the opening and closing of pipelines and pressure release systems. They also support railroad cars and engines, and are used in bridges and overpasses. In environments prone to vibrations or motion, coil springs function as dampeners and sound-absorbing devices to protect and enhance the durability of applications.

Firearms Uses

Coil springs are essential components in firearms, found in magazine springs, trigger springs, and recoil springs. In detonators, they are compressed and held in a flattened state until activation. Their reliability and durability make them suitable for the constant use demanded by loaded weapons.

Residential Use

The average home contains a multitude of coil springs in nearly every room. They are found in mattresses, chairs, and couches to provide support and absorb impact. Modern children’s toys use springs to activate their functions and keep them operational. Coil springs are also crucial in switches, garage door openers, cabinets, appliances, and countless other applications. In many ways, homes rely heavily on coil springs for smooth and effortless living.

Springs in Pens

Compression coil springs are employed to extend and retract the ballpoint of a pen. These springs need to be elastic enough to compress to a solid height. For proper functionality, the spring must have a suitable index and an adequate number of coils relative to its free length and wire diameter. Generally, a larger diameter and more coils result in a lighter spring.

Types of Compression Coil Springs for Ballpoint Pens

Conclusion

The three main types of coil springs are compression, extension, and torsion, each of which performs a different function.
The most common type of coil spring are compression springs, which are produced by hot or cold winding spring steel.
The production of coil springs includes using a coiling mechanism to form a helical shape.
The first step in the manufacture of coil springs is the selection of the appropriate metal from which to fabricate the springs. Critical to the selection process is the tensile strength of the metal such that it conforms to the demands of the application.
Coil springs have a coiled appearance and are made from a single strand of metal that follows a helical path to create the coil. The most common method to manufacture coil springs is to wrap wire material of varying diameters around a mandrel, arbor, or cylindrical tubing.