Precision compression, extension and torsion springs for industrial applications.
SPRINGS
Extension Springs Manufacturer for Industrial & OEM Applications
Custom extension springs designed for consistent load performance, reliable hook strength, and long service life.
At Super Springs, we work with engineers and procurement teams who need reliability — not just samples that work once, but parts that perform consistently in production.
From light precision springs to heavy-duty industrial assemblies, we manufacture extension springs tailored to your exact design, load and hook configuration requirements.
What Are Extension Springs
Extension springs (also called tension springs) are close-coil helical springs designed to resist a pulling force. The coils are wound tightly together in their natural state. When a load is applied, the spring stretches and stores energy. Once the load is removed, it returns to its original length.
They are distinguished from compression springs by their end hooks or loops, which attach to the assembly and transfer the tension load into the spring body
Key Extension Spring Design Parameters
A well-designed extension spring depends on multiple factors. We work closely with your design inputs to ensure performance is predictable and repeatable.
Key extension spring design parameters include:
• Wire diameter (d)
• Outer diameter (OD)
• Free length — total length including hooks, unloaded
• Number of active coils
• Hook type — end configuration at each end
• Angle between hooks — orientation of the two hooks relative to each other
• Load and deflection requirements
• Spring rate (N/mm)
Please read our article about Specifying a custom Spring - 8 parameters you must get right. If you are working on calculations, you can also use our Spring Rate Calculator to estimate performance during the design stage.
Hook End Types Available
choice of hook type affects load transfer, fatigue life and ease of installation.
We manufacture extension springs with the following 8 hook configurations:
• Closed German Loop — the most common loop type; the coil end forms a full closed loop
• German Side Loop — loop offset to the side of the coil centreline
• Raised Hook — hook raised above the coil centreline for clearance in the assembly
• Half German Hook — open loop, used where a closed loop cannot be inserted
• Double German Loop — double loop for higher load capacity at the hook
• Extended German Side Loop — extended side loop for longer reach
• English Loop — full loop with an offset, commonly used in UK and European assemblies
• Extended Side Hook — raised hook offset to the side, for specific assembly geometries
When ordering, specify the required hook type for each end and the angle between the two hooks if orientation is critical to your assembly. If you are unsure which hook type is suitable, share your drawing or application details and we will recommend the correct configuration.
Materials Used
Material selection plays a critical role in spring performance, fatigue life and corrosion resistance.
We commonly manufacture extension springs using:
• Spring Steel SM/DM (medium carbon) — general purpose industrial applications
• Spring Steel SH/DH (high carbon) — higher load, agricultural equipment and high cycle applications
• Stainless Steel SS304 — corrosion resistance, suitable for outdoor, food contact and humid environments
• Stainless Steel SS316 — for aggressive corrosive environments and marine applications
• Music Wire (EN 10270-1) — high strength, suitable for precision and electronic applications
• Oil Tempered Wire (EN 10270-2) — suitable for dynamic and heavy-duty applications
Material selection is always aligned with your application requirements. If you are unsure which grade to specify, share your operating environment details and we will recommend the correct material.
Manufacturing Capabilities
We focus on manufacturing consistency — especially important for OEM supply.
Our capabilities include:
• Wire diameters from 0.3 mm to 6 mm
• 8 hook end configurations (see hook types section above)
• Precision-controlled CNC coiling machines
• Tight dimensional tolerances
• In-house load testing for precision manufacturing
• Heat treatment for strength and durability
• Surface finishing options — zinc white plating, zinc black, powder coating, passivation
• Low MOQ for prototypes and new product development
• High-volume production capability for ongoing OEM supply
Whether you need prototypes or ongoing production, the goal remains the same — reliable output, batch after batch.
Wire Grades and Customisation — Manufactured in India
Our extension springs are manufactured at our factory in Gurgaon, India in spring steel grades SM/DM and SH/DH, along with SS304 stainless steel for corrosive or outdoor applications.
To order a custom extension spring, provide: wire diameter (d), outer diameter (OD), free length including hooks (L), number of active coils (N), hook type and angle between hooks — or simply send a drawing or sample.
We supply automotive, agricultural, industrial machinery and hardware sectors with consistent quality across bulk production runs. 40+ years of manufacturing. ISO 9001:2015 certified. Exporting to 14 countries.
Applications
Extension springs are used across a wide range of industries:
• Automotive — door mechanisms, boot hinges, seat return assemblies
• Agricultural equipment — implement linkages, return mechanisms, hitch assemblies
• Garage and commercial doors — counterbalance and return spring systems
• Industrial machinery — conveyor tension systems, safety return mechanisms
• Exercise and fitness equipment — resistance mechanisms
• Consumer products — screen doors, access panels, tool mechanisms
• Electrical and electronic assemblies — precision instrument springs
Each application comes with its own load, space, hook type and durability requirements — and the design must reflect that.
Surface Treatments
Surface treatment provides corrosion protection and, in some applications, improves fatigue life.
• Zinc white plating — standard finish for indoor and mild outdoor applications
• Zinc black — same protection with a black appearance
• Powder coating — for colour matching and enhanced outdoor protection
• Passivation — for stainless steel springs, enhances corrosion resistance
• Shot peening — improves fatigue life for high-cycle applications
• No coating — for lubricated or internally protected assemblies
For export to humid climates — Middle East, Southeast Asia, West Africa and Latin America — zinc white plating is recommended as a minimum.
Custom Extension Springs
Most applications require customisation — and that is where we focus.
We support:
• Manufacturing to drawing — any format including PDF, DXF, STEP or hand sketch
• Design-based requirements — provide load, space constraints and service life
• Sample replication — send us a physical sample and we measure and replicate it
• Prototyping and development — low MOQ for new product development
• OEM supply — consistent bulk production for ongoing programmes
The goal is not just to make springs, but to ensure they work reliably in your system.
The spring rate (k) of a compression spring is calculated using:
k = Gd⁴ / 8nD³
Where:
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G = shear modulus
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d = wire diameter
-
n = number of active coils
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D = mean coil diameter
You can also use our Spring Rate Calculator for quick estimation.
Over time, we’ve realised that most customers are not looking for a “vendor” — they’re looking for a dependable manufacturing partner.
What matters to them:
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Consistency across batches
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Predictable performance
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Clear communication
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Long-term reliability
That’s exactly what we focus on.
Frequently asked Questions
What materials are used for extension springs?
Extension springs are typically manufactured in spring steel SM/DM, SH/DH, stainless steel SS304 or SS316, music wire or oil tempered wire depending on the application load, cycle life and operating environment.
How many hook types are available?
We manufacture extension springs with 8 hook configurations: Closed German Loop, German Side Loop, Raised Hook, Half German Hook, Double German Loop, Extended German Side Loop, English Loop and Extended Side Hook. Custom hook angles are also available.
What wire diameter range do you manufacture in?
We manufacture extension springs from 0.3 mm to 6 mm wire diameter. For wire diameters above 6 mm in tension applications, our drawbar springs range covers heavy-duty requirements.
What tolerances can be achieved?
Tolerances depend on the design and wire size, but we maintain tight control to ensure consistent performance in production. In-house load testing is carried out for precision applications.
How is spring rate calculated?
Spring rate depends on material, wire diameter, coil diameter and number of active coils. Use our Spring Rate Calculator for quick estimation, or contact us and share your load and deflection requirements.
Can you manufacture to a drawing or sample?
Yes. We accept drawings in any format — PDF, DXF, STEP or hand sketch — as well as physical samples. We measure, specify and manufacture to match. Low MOQ prototype orders are available before bulk production commitment.
