Stock Extension Springs - Over 4,000 Different Designs
Torsion Springs
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Stock Extension Springs: Over 4,000 Different Designs
Table of Contents
Designed to store energy and exert a pulling force when stretched, stock extension springs consist of helical coils tightly wound without pitch. These components extend to a precise length upon the application of force to their ends, supplying critical tension for diverse applications ranging from heavy-duty machinery to high-precision medical instruments.
Why choose a stock extension spring for your project?
If you are prototyping a new project, ordering five different variations of a custom spring means paying five different manufacturing setup fees. For a small R&D department or a solo designer, these costs can easily climb into the thousands of dollars before you’ve even finalized a design. It’s a budget-killer that often stalls innovation.
By choosing from our catalog of over 4,000 stock designs, you skip those setup charges entirely. We offer small quantities for engineers, allowing you to "fail fast" and iterate your design until the tension and travel are exactly where they need to be. Think of our stock inventory as your personal hardware laboratory; you can order a handful of different wire diameters or lengths today and have them on your workbench by the end of the week.
Quality You Can Trust: Made in the USA & ISO Certified
When you are designing a product that people rely on, "good enough" wire just doesn't cut it. We understand that B2B buyers, procurement officers, and lead engineers need more than just a part; they need accountability and peace of mind. That is why our stock extension springs are Made in the USA and produced in facilities that maintain ISO 9001:2015 certification. These aren't just logos on a page; they are a guarantee of material traceability, dimensional consistency, and the high-tensile reliability that keeps global assembly lines moving. When you buy from our catalog, you are buying a component that meets rigorous international quality standards, ensuring that the thousandth spring you pull from the box performs exactly like the first.
How do you find the right spring among 4,000 designs?
I know a massive catalog can feel like looking for a needle in a haystack, so we’ve built a sophisticated Online Stock Extension Spring Finder to act as your digital GPS. If you have your specs ready, you can perform a basic search using just the Outer Diameter (OD) and Length Inside Hooks.
For the seasoned engineer who needs to hit a specific "sweet spot," our advanced search allows you to filter by:
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Material Type: Choose from Music Wire, Stainless Steel 302, Beryllium Copper, or Phosphor Bronze, among others.
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Initial Tension: The internal force that holds the coils together.
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Spring Rate: How much force is required to extend the spring one inch.
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Maximum Safe Travel: To ensure you don't overstretch and permanently deform the wire.
Not sure which one to pick? > Pro Tip: Use our "Add to Compare" feature. Select up to three different springs, and we’ll show you their specs side-by-side in a clean table. It’s the easiest way to see the subtle differences in load capacity before you hit "buy."
Which hook type does your application need?
In my experience, the hook is the most overlooked part of spring design, yet it’s the primary point of failure if chosen incorrectly. The hook is the "handshake" between the spring and your machine; if the grip is wrong, the whole system fails, often leading to unhooking, bending, or premature fatigue at the "rise" (the point where the wire transitions from the coil to the hook).
To make your shopping experience more intuitive, we’ve categorized our 4,000+ designs by their end types, allowing you to jump straight to the results that match your mounting hardware:
Machine Hooks: These are the gold standard for general engineering. Formed by a single loop of wire at the same diameter as the spring body, they offer a secure, cost-effective connection for everything from carburetors to gym equipment. They are sturdy, reliable, and the most common choice for standard industrial use.
Crossover Center Hooks: If you’ve ever had a spring "twist" or pull unevenly, you need these. By bending the wire across the center of the coil before forming the loop, the tension is distributed perfectly along the axial centerline. This reduces side stresses on your mounting pins and significantly extends the life of the spring by preventing the "twisting" motion that can cause premature snapping.
Side Hooks: In many modern compact designs, there simply isn't room for a centered hook. Side hooks allow the spring to lay flat against a chassis or plate, making them the "low-profile" heroes of the spring world. They sit off to the side of the coil diameter, perfect for sliding into a small hole on a flat metal sheet.
Extended Hooks: Sometimes, the design calls for high tension, but the anchor points are inches apart. Rather than using a long, "lazy" spring that loses its force quickly, extended hooks allow you to use a powerful, short coil body to reach across the gap. These are common in heavy machinery where the mounting point is recessed or hard to reach.
How do you measure an extension spring accurately?
Before you reach for your calipers, you need to know exactly what points to measure. I’ve seen many frustrated engineers order the wrong part because they measured the "Overall Length." In the spring industry, we focus on the functional length. If you are looking to replace a broken spring or match a design, follow these three critical steps:
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Wire Diameter: This is the most crucial measurement for strength. Measure the thickness of the wire itself using a micrometer or digital calipers. Even a difference of .005" can drastically change the spring's rate (how "stiff" it feels) and its load capacity.
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Outer Diameter (OD): Measure the widest part of the coil body. This is vital if your spring needs to fit inside a tube or pass through a hole. Ensure you measure at several points along the body to account for any slight bowing in a used spring.
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Length Inside Hooks: This is the industry standard for "Length." Instead of measuring from tip to tip, you measure from the inside bearing point of one hook to the inside of the other. This tells you exactly how much space the spring occupies when it's just sitting on its mounting pins without any tension.
Wait, there’s more than just size! Beyond the physical dimensions, you should consider Initial Tension. This is the internal force that keeps the coils pressed together. If you’ve ever tried to pull a spring and it didn't budge at first, that’s initial tension.
If you are starting with a blank slate and don't have a physical spring to measure, don't guess. Try our Spring Creator. It’s a free online calculator that generates live blueprints and full mechanical analyses. It even provides warnings if your design is physically impossible or likely to break, acting like a digital mentor over your shoulder to ensure your prototype works on the first try.
Can't find the exact size? Try our common shortcuts!
Sometimes, looking at a thousand options is paralysis by analysis. If you are in a rush, or if you are replacing a part on a common piece of machinery, you likely need one of the "industry standards." We’ve created these "Shop by Popular Sizes" shortcuts to get you to your part in seconds rather than minutes:
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Shop 1/4" OD Springs: These are the favorites for precision electronics, small-scale robotics, and hobbyist projects. They offer a delicate touch without sacrificing reliability.
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Shop 1/2" OD Springs: If you’re fixing something in the garage, a household appliance, or a piece of plant equipment, start here. This is the "Universal Workhorse" of extension springs, thick enough for significant loads but small enough to fit almost anywhere.
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Shop 1" Length Springs: When you have a tiny footprint but need a lot of pull, these short-body springs provide high tension over a very limited distance.
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Shop Stainless Steel 302 ASTM A313: Don't let rust ruin your design. If your spring is going to be used outdoors, in a marine environment, or in a medical setting, these corrosion-resistant shortcuts are your best friend.
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Shop Music Wire ASTM A228: For the highest tensile strength and the best performance in "dry" indoor environments, our Music Wire shortcuts lead you to the toughest springs in the catalog.
Master Your Tension
Navigating the world of tension doesn't have to be a headache. Whether you are buying a single replacement for a broken lawnmower or a thousand units for a new product launch, here is the essential guide to making an informed decision:
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Cost-Effective Prototyping: Leverage our stock inventory to test multiple variations without incurring expensive custom setup fees.
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Technical Filtering: Use the advanced Spring Finder to sort by material (like Music Wire or Stainless) and specialized finishes (Zinc or Black Oxide).
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Hook Geometry is Key: Ensure your hook type—be it Machine, Side, or Cross Over—matches your mounting points to prevent premature wear.
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The Quality Standard: Trust in ISO 9001:2015-certified, USA-made products to ensure your project stands the test of time.
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Side-by-Side Comparison: Use the "Compare" tool to weigh the pros and cons of different spring rates and load capacities before committing.
Still feeling stuck in the coils? Our team of experts lives and breathes spring physics every single day. If your application is unique, requires exotic materials, or needs a custom-engineered solution that isn't in our 4,000+ design catalog, contact our experts today. We’re here to help you get the tension exactly where it needs to be!
Contact our engineering team today:
Phone: (951) 276-2777
Email: sales@acxesspring.com
Invest in precision and quality
Spring Creator 5.0 offers you the possibility to design springs that perfectly fit your needs. Our platform not only allows you to design various types of springs but also provides advanced tools like the Online Spring Force Tester to simulate and evaluate spring performance. Visualize your design in 3D, download detailed blueprints, and get instant quotes. Try it for free and discover why we are the preferred choice of engineers and makers!
Created by Alfonso Jaramillo Jr
President Acxess Spring
Over 40 Years of Experience in Spring Engineering and Manufacturing