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Definition:
Helically wound wires which form a spring. They are made to absorb or eject an energy or force.
Helical springs are also known as compression springs and are the most common type of spring in the market. Acxess Spring makes custom helical springs but also provides its customers with a wide range of stock helical compression springs through our online store, The Spring Store. You are able to find your helical springs by only inputting either outer or inner diameters along with the free length you desire your helical spring to have.
In case you are unsure of your helical spring’s physical dimensions, you can use our easy to read how-to-measure diagram to the left. The best way to measure a helical spring is using a dial or digital caliper. To accurately measure your helical spring’s dimensions, follow the instructions provided below:
- Outer Diameter: Vertically place the spring between the caliper’s outside jaws and make sure that they are perfectly aligned with the axis (center) of your spring’s cylindrical shape
- Inner Diameter: Place the caliper’s inside jaws inside your spring’s inner diameter while your spring is put at its vertical position
- Wire Diameter: Keeping your spring vertical, place the caliper’s outside jaws on the outer edges of the wire diameter
- Free Length: Horizontally place the helical spring between the caliper’s outside jaws. Make sure you are including the whole part of the spring without leaving any edges sticking out
- Total Coils: Count your spring’s coils by looking at your spring horizontally with the tip of the first coil aligned at the center. Begin counting from the second coil and stop at the last coil
Helical springs also have different end types because some ends may provide the helical spring more stability while others will provide more flexibility. The types of ends are the following:
- Closed Ends: Most common end type
- Ground Ends: Made to provide stability in case a spring has the risk of tipping over when placed vertically on a flat surface
- Double Closed Ends: Also made to provide stability but in this case they are used when the spring design has a risk of buckling
- Open Ends: All coils are active, therefore giving the helical spring less force but more travel as well as reducing your spring's solid height
A helical spring is a coil of metal wire wound in the shape of a helix (like a corkscrew). Thanks to this coil shape, a helical spring can be compressed under load (squeezed shorter) and will push back against that force. When the load is removed, the spring returns to its original length, ready to be compressed again. In other words, they absorb, store, and release energy or force by deforming under pressure and springing back when released. This ability to “spring back” makes them invaluable as shock absorbers, force regulators, and energy storage devices in innumerable applications.
Acxess Spring specializes in helical compression springs. We manufacture custom helical springs for specific applications and also maintain a huge inventory of stock compression springs available for immediate purchase. In fact, our online catalog contains over 35,000 stock spring designs ready to ship. Whether you need a single replacement spring for a DIY project or a bulk order for an engineering prototype, we likely have a stock spring that fits your needs. And if we don’t, we can make it! Before we get into how to buy or custom-order these springs, let’s first make sure you know how to identify and measure the key characteristics of a helical spring.
If you have an existing spring (or a design in mind) and want to find a matching replacement or specify a new one, it’s crucial to measure the spring’s dimensions accurately. Even if you’re new to this, don’t worry, measuring a helical compression spring is straightforward with the right tool and a bit of guidance. The only tool you really need is a caliper (a digital or dial caliper works best for precision). Below are the main dimensions and characteristics you should measure or determine for your spring:
Outer Diameter (OD): This is the diameter of the outside of the spring’s coils. To measure the outer diameter, hold the spring vertically and place the caliper’s outside jaws around the widest point of the spring’s coil. Make sure the jaws are aligned straight across the center of the spring’s circular cross-section for an accurate reading. The caliper reading will give you the outer diameter of the spring.
Inner Diameter (ID): The inner diameter is the width of the open space inside the spring’s coils. You can measure this by inserting the caliper’s inside jaws into the spring (still holding the spring vertically) and opening them until they touch the inside edges of the coil. If you have the outer diameter and the wire diameter (see next step), you can also calculate the inner diameter as ID = OD – 2 × wire diameter. But measuring it directly with the caliper ensures accuracy, especially if the spring’s wire is thick.
Wire Diameter: This is the thickness of the wire that the spring is made from. To measure the wire diameter, place the caliper’s outside jaws on a single coil’s wire (essentially measuring the thickness of the wire itself). It’s often easiest to do this while the spring is vertical, touching the jaws to the outer surface of the wire on each side. Be careful to only measure the wire and not any gap between coils. Wire diameter is important for calculating spring strength, and also for determining the inner diameter if you know the outer diameter.
Free Length: The free length is the overall length of the spring when it is not under any load (i.e., its natural, fully extended length). To measure free length, lay the spring on a flat surface or hold it horizontally, and use the caliper’s outside jaws to measure from one end of the spring to the other. Ensure you include the entire end of each coil in the measurement (no coils sticking out past the jaws). Free length is critical for understanding how much space the spring will occupy and how far it can compress.
Total Coils: Count how many coils the spring has from one end to the other. This can sometimes be tricky, especially if the ends of the spring are finished in a certain way (more on end types soon). A good method is to hold the spring horizontally at eye level. Start with the first full coil at one end: align that coil at the center of your view, then count each full rotation of the coil all the way to the other end. Don’t count the same coil twice, and stop when you reach the last coil at the opposite end. The total coil count often includes any partial coils at the ends if the ends are closed (again, we’ll discuss end types next). Knowing the total number of coils is useful for spring design and can affect the spring’s rate and solid height.
By carefully measuring these parameters, you will have a clear “fingerprint” of your spring. It’s best to write down these measurements (in either inches or millimeters, noting which unit you used). Once you have these details, you’re ready to find a matching spring. If any of the terms above are new to you, rest assured that our Spring Finder tool will prompt you for these inputs in a friendly way, and even has hints and diagrams to help you along. Next, we’ll talk about spring end types, which you should also be aware of when identifying or specifying a helical spring.
Not all compression springs look exactly the same at the ends. The end type of a helical spring refers to how the coils are finished at the top and bottom of the spring. The end type affects how the spring sits in an assembly and can influence the spring’s stability, total coils, active coils, and solid height. Choosing the right end type is important for your spring’s performance. Here are the common helical spring end types and what they mean:
Closed and Squared Ends: This is the most common end type. A spring with closed ends has the last coil at each end wound so that it touches or nearly touches the previous coil, effectively “closing” the end. This creates a relatively flat surface for the spring to sit on. Closed ends improve stability compared to a raw cut end and distribute force evenly. Most stock compression springs you encounter will have closed ends by default.
Close and Ground Ends: In this type, the end coils are closed and then ground flat. Imagine taking a closed-end spring and shaving the end until it’s perfectly flat and perpendicular to the spring’s axis. Ground ends provide excellent stability, especially when a spring must stand upright on a flat surface without wobbling. If your spring will sit in a freestanding position or against a flat plate, ground ends ensure full contact and reduce the risk of the spring “tipping over” under load. (Ground ends are essentially an upgrade to closed ends for critical applications.)
Double Closed Ends: This configuration provides maximum stability. Here, two coils at each end are closed (so each end has an extra coil wound tight against the previous one). In total, you get four closed coils (two on each end) in the spring. Double closed ends are used for springs with a high slenderness ratio (long and thin springs) where there’s a risk of buckling or bending sideways under compression. By having two coils firmly together at the ends, the spring has a more stable platform on each side, helping it stay straight. The trade-off is a slightly taller solid height and a bit more inactive coil length, but the added stability can be crucial for certain designs (particularly long springs).
Open Ends: An open-ended spring has no special treatment on the last coils, they are left with the same pitch (spacing) as the active coils. This means all coils are active with none touching at rest. The benefit is increased flexibility: an open-ended spring can compress further (longer travel) and typically has a lower spring rate (so it’s “softer”). Open ends also result in a shorter solid height when fully compressed, because there are no closed coils taking up extra space. However, open ends provide the least stability. The spring’s ends are not flat, so the spring may not sit perfectly upright without a guide. Open-ended springs are useful when you need maximum deflection and when the spring is confined in an assembly that guides its position.
The easiest way to find the right stock spring is by using our Spring Finder 5.0 tool. Spring Finder is a powerful search engine for our spring catalog. All you need to do is enter the dimensions you have (even if it’s just a couple of key specs like OD and Free Length), and Spring Finder will instantly filter through our stock compression springs to show you matches. You can even set min/max ranges or switch between metric and imperial units with a click, making it convenient for anyone to use. The result is a list of springs you can choose from, complete with detailed specs. Once you spot the spring that looks right, just add it to your cart and proceed to checkout. It’s that simple to buy a stock helical spring online.
Ready to find your spring? Give Spring Finder a try. Enter the dimensions you’ve measured, and see instant results from our extensive Acxess Spring catalog of stock springs. With just a few clicks, you can have the perfect spring on its way to you. And if you need any assistance during the process, our team is just a phone call or email away to help!
Sometimes, a stock spring might not meet your needs, maybe you have unique size requirements, a special material in mind, or need a large quantity for production. Fear not: Acxess Spring’s custom spring manufacturing has you covered. We pride ourselves on being a one-stop spring supplier, which means we’ll make the exact custom helical spring you need, built to your specifications with quality and precision.
The quickest way to design and quote a custom spring is to use our online Spring Creator tool (part of our website’s suite of engineering tools). Spring Creator 5.0 is a free online spring calculator that lets you input your desired specifications for a compression spring (as well as other spring types). It’s very user-friendly: you enter the dimensions and performance requirements you have (such as the loads or spring rate you need), and it will automatically generate a full spring design analysis. You’ll see all the technical details of the design (spring rate, stress levels, solid height, etc.), essentially letting you verify that the spring will work for your application.
Not comfortable designing it yourself? No problem! We’re here to help. You can always contact our spring experts directly with your requirements. Email us or give us a call, we often assist customers by reviewing drawings or even reverse-engineering a spring from a physical sample. For more complex designs (for example, a spring with an unusual shape, or if you need a material that isn’t listed in our online tool, or quantity beyond the tool’s limits), our team will handle your request personally. We can work with specialized materials and large orders; just let us know what you need. Our goal is to make the custom spring process as easy and transparent as buying a stock spring. Your perfect spring is just a design away!
Now that we’ve covered all the basics: what helical springs are, how to measure and specify them, the end types to consider, and how to purchase stock or custom springs, you should be well-equipped to make an informed decision. In case you need a quick recap, below we’ve highlighted the key takeaways from this guide. We hope this article has demystified the process and shown that finding the right spring isn’t daunting at all. Acxess Spring is here to help at every step, from research to purchase. Let’s wrap up with the main points to remember:
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Helical Spring Basics: A helical spring is a coiled wire that compresses under load and springs back when the load is removed. It’s the most common spring type, also called a compression spring, used to absorb and release energy in countless applications. Acxess Spring offers expertise in these springs, positioning us as both a technical authority and a convenient supplier for all your spring needs.
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Measuring Springs Made Easy: You can identify a spring’s specifications by measuring its wire diameter, outer (or inner) diameter, free length, and total coils using a simple caliper. Getting these dimensions right is crucial for finding a matching spring. Remember to also note the spring’s unit of measure (inches or mm) and any performance info like spring rate if available. Knowing how to measure a spring empowers you to use our tools effectively and ensures you get a proper fit when ordering.
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Understanding Spring End Types: End configuration matters. Whether you need closed & squared ends for general stability, ground ends for extra-flat stability, double closed ends to prevent buckling, or open ends for maximum flexibility and travel, choosing the right end type will impact your spring’s performance (like stability and solid height). This guide covered the differences so you can specify the end type that best suits your application.
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Find & Buy Stock Springs Online: For standard sizes, buying helical springs online is fast and convenient. Through The Spring Store (Acxess Spring’s online catalog of over 30,000 stock springs), you can use the Spring Finder tool to input your dimensions and instantly locate in-stock springs that meet your needs. Each product page provides detailed technical data so you can buy with confidence. Our stock springs are ready to ship in days, getting your project up and running quickly, just add to cart and purchase online, no fuss.
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Custom Springs and Expert Support: If a stock spring won’t do, Acxess Spring’s custom spring manufacturing has you covered. Use our Spring Creator tool to design your perfect spring and get an instant quote (with surprisingly quick lead times of only a few weeks for production). You’re never alone in the process, our spring experts are available to answer questions, give advice, and ensure your custom spring is exactly right. Contact our team at any time for friendly, professional help. We make the custom ordering process as approachable as buying stock, so you can get a tailor-made solution with ease.
Feel free to reach out to Acxess Spring for any of your helical spring needs, whether it’s selecting a part from our extensive catalog or designing a new spring from scratch. We’re here to help you move from research to purchase confidently and quickly. Happy spring sourcing, and we look forward to being your trusted spring supplier!