Custom Extension Springs - Industrial Grade Tension Springs Manufacturing

Custom Extension Springs — Made to Your Drawing, Built for Production

We manufacture custom extension springs with precise initial tension, controlled load characteristics, and batch-to-batch consistency. From sampling to mass production, every spring is engineered for your specific application requirements.

Fast prototyping, in-house quality control, and export-ready packaging — all from one factory, delivered door-to-door.

Get Engineering Quote Send Drawing (Confidential)

Made to Print

Batch Consistency

Export-Ready Packaging

How Buyers Typically Come to Us for Extension Springs

Whether you have complete drawings, physical samples, or just an application challenge — we have a process to help you get the right spring.

Drawing-Based Inquiry

You have drawings or specifications

You already have technical drawings, CAD files, or defined parameters. You need a manufacturer who can confirm manufacturability, validate performance expectations, and ensure batch stability.

Verify load and deflection calculations
Confirm material and surface treatment suitability
Get accurate lead time and pricing
Ensure long-term supply consistency

Upload Drawing

Sample-Based Reverse Engineering

You have a physical sample

Your original supplier stopped production, or quality has become inconsistent. You have a physical sample but no documentation. We measure, analyze, and recreate the spring to match or improve on the original.

Precision measurement of all dimensions
Material identification and testing
Load curve verification
Documentation for future orders

Send Sample Photo

Application-Based Consultation

You have an application challenge

You know what the spring needs to do, but not the exact specifications. Share your application requirements — mounting space, load range, environment, cycle life — and our engineers will help define the parameters.

Application environment analysis
Load and deflection requirement definition
Material and hook type recommendation
Prototype for real-world testing

Describe Application

What Is an Extension Spring — And Why Specifications Matter

Extension springs, also called tension springs, store energy by being stretched rather than compressed. Unlike compression springs, they are wound with initial tension — a preload force that holds the coils together before any external load is applied. This initial tension is what defines how the spring behaves at rest and determines the force required to begin extension.

The performance of an extension spring depends entirely on getting the specifications right: wire diameter affects fatigue life and load capacity; free length and number of coils determine the working range; hook type affects durability and mounting options. Small errors in load calculation or material selection often lead to early failure — not just spring failure, but system-level problems that can be misdiagnosed as design flaws.

Common procurement mistakes: Specifying only outer diameter and free length without defining initial tension or working load points. Ignoring the hook-to-body transition (a common stress concentration point). Choosing materials without considering the operating environment. These oversights lead to springs that "look correct" but fail in service.

The difference between a spring that lasts and one that fails prematurely often comes down to these specification details — details that require both engineering knowledge and manufacturing experience to get right.

Not Sure Which Spec to Start With? Ask an Engineer

Where Extension Springs Are Commonly Used

Extension springs serve critical functions across industries — from recreational equipment to agricultural machinery. Each application has unique requirements for load, environment, and cycle life.

Trampoline Springs

High cycle fatigue, safety-critical. Requires consistent tension across all springs in the set.

Drawbar Springs / Towing Systems

Shock absorption under heavy loads. Corrosion resistance for outdoor exposure.

Garage Door Mechanisms

High cycle counts (10,000+ cycles). Safety and lifespan are critical.

Industrial Equipment Return Mechanisms

Precise return force. Stable performance over extended operation.

Agricultural Machinery Linkages

Mud, water, debris exposure. Corrosion resistance essential.

Material Handling / Conveyors

Continuous operation. Consistent tensioning over millions of cycles.

Power Tools / Hand Tools Recoil

Space-constrained. High force in compact form factor.

Automotive Under-Hood Mechanisms

Temperature extremes. Oil/chemical resistance required.

Fitness Equipment Tension Systems

High fatigue frequency. Batch consistency for uniform feel.

HVAC Dampers / Latches

Quiet operation. Long-term durability in climate systems.

Garage Door Systems

Agricultural Machinery

Fitness Equipment

Automotive Components

Tell Us Your Application → Get Material & Hook Suggestion

Extension Springs - Redesigned Modules

Material Options for Extension Springs

Material selection should be driven by your operating environment, not just load requirements. Indoor climate-controlled applications have different needs than outdoor machinery exposed to moisture, chemicals, or temperature extremes.

Music Wire (ASTM A228)

Best for: Indoor, dry environments

Highest tensile strength of common spring materials. Excellent fatigue life for high-cycle applications. Most cost-effective for general-purpose springs.

⚠️ Not suitable for outdoor use without surface treatment — will rust quickly

Oil Tempered Wire

Best for: Higher stress applications

Better performance under higher stress than music wire. Good for automotive and industrial applications where springs see sustained loading.

⚠️ Still requires surface treatment for corrosion environments

Stainless Steel 302/304

Best for: Mild corrosion, food/medical

Good corrosion resistance for mildly corrosive environments. Common in food processing, medical devices where rust contamination is unacceptable.

⚠️ Lower strength than music wire — may need larger wire diameter

Stainless Steel 316

Best for: Marine, chemical exposure

Superior corrosion resistance, especially against chlorides. Essential for marine applications, chemical processing, and coastal installations.

⚠️ Higher cost than 302/304 — use only when environment requires it

Galvanized Wire

Best for: Outdoor, moisture exposure

Cost-effective corrosion protection for outdoor applications. Zinc coating provides sacrificial protection. Good for agricultural and construction.

⚠️ Coating may wear at contact points — consider for lower-cycle applications

Phosphor Bronze

Best for: Electrical, non-magnetic

Excellent electrical conductivity and corrosion resistance. Non-magnetic. Used in electrical contacts and switches.

⚠️ Lower strength — typically for lighter loads only

Tell Us Environment → Get Material Recommendation

Different Hooks for Extension Springs — Choose by Mounting & Load Direction

The hook is often the weakest point of an extension spring. Selecting the right hook type for your mounting method and load direction is critical for reliability and safety.

Machine Hook

Standard hook formed from last coil. Cost-effective for general applications with axial loading.

C-Hook / Side Hook

Hook opens to the side. Used when hook must engage from a perpendicular direction.

Extended Hook

Longer hook reach for engaging distant mounting points. More installation flexibility.

Swivel Hook

Allows rotation during operation. Reduces stress from misalignment or angular movement.

V-Hook

V-shaped opening for secure engagement on pins or rods. Good retention under vibration.

Center Hook

Hook aligned with spring centerline. Reduces bending stress for pure axial loading.

Double Loop / Full Loop

Closed loop on each end. Maximum strength but requires threading through mounting hardware.

Threaded Insert

Threaded end for screw-in mounting. Precise adjustment and secure attachment.

Why Hook Selection Matters

The hook-to-body transition is the most common failure point in extension springs. Stress concentration at this transition causes most extension spring failures — not coil breakage. When selecting a hook type, consider: installation space and access, load direction (axial vs. angular), rotation requirements, wear at contact points, and whether the application requires a safety closure to prevent disengagement.

Send Mounting Photo → We Suggest Hook Type

How We Control Quality — Not Just Claim It

Quality control isn't a checkbox — it's a process embedded at every stage from incoming material to final packaging.

Precision Load Testing

Verifying tension and load characteristics at specified deflection points

Incoming Material Verification

Wire diameter, tensile strength, and material certification review

Incoming Wire Inspection

Material certificates verified, wire diameter and tensile strength sampled

In-Process Checks

Dimensions, hook formation, free length checked during production

Load Testing

Initial tension and load at specified deflection verified on testing equipment

Fatigue Testing

Cycle life validation available for critical applications requiring documented endurance

Batch Records

Traceability from wire lot to finished product for every production batch

View Quality Control & Testing Need Inspection Report?

Real Products, Real Factory

Hook End Inspection

Quality check on hook formation and transition

Sample Board

Organized samples for customer approval

Pre-Assembly State

Springs grouped and oriented for line delivery

Shipping Packaging

Export-ready cartons with custom labeling

CNC Spring Coiling

Precision automated coiling process

Wire Material Storage

Organized raw material inventory

Production Line

High-volume manufacturing capability

Heat Treatment

Stress relieving for optimal performance

Dimensional Inspection

Precision measurement verification

Surface Treatment

Zinc plating and coating processes

Final Assembly

Pre-assembly and kitting services

Quality Lab

Testing and certification facilities