Extension Springs

  • .007 to .625 Inches In Spring Wire Diameter
  • Custom Extension Spring End Options to Meet Your Needs
  • Round, Rectangular, Square & Special-Section Wire

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Extension Spring Manufacturing Specifications

While we have listed some of the most common sizes, materials and manufacturing specifications, Newcomb Spring provides completely customized production of all springs and metal forms.

Extension Spring Shapes & Sizes

  • .007 to .625 Inches in Wire Diameter
  • Up to 2.0 Inches Bar Stock
  • Round Wire
  • Square Wire
  • Rectangular Wire
  • Special Section Wire

Spring End Types

  • Cross Center Hooks / Cross Loops
  • Draw Bars
  • Extended Machine Hooks
  • Expanded Hooks
  • Standard Machine Hooks
  • Rectangular Ends
  • Rectangular Ends with Swivel Hooks
  • Teardrop-Shaped Ends
  • Threaded Inserts
  • V-Hooks

Common Materials for Extension Springs

  • Spring Steel
  • High Carbon Steel
  • Low Carbon Steel
  • Nickel Plated Carbon Steel
  • Stainless Alloys
  • Non-Ferrous Metals
  • Elgiloy®
  • Hastelloy®
  • Monel®
  • Inconel®
  • Titanium
  • and More

Extension Spring Initial Tension

Most extension springs are wound with initial tension. This is an internal force that holds the extension spring's coils together. The measure of the initial tension is the load necessary to overcome the internal force and begin coil separation. Unlike a compression spring that has zero load at zero deflection, an extension spring can have a preload at zero deflection (see graph). This built-in load, called initial tension, can be varied within limits, decreasing as the spring index increases.

Note that there is a range of stress (and, therefore, force) for any extension spring index that can be held without problems. If the designer needs an extension spring with no initial tension, the spring should be designed with space between the coils. Read more on initial tension.

Initial Tension (P1) is determined by extending the extension spring to a given length (L1) ensuring coil separation. The spring then is extended an equal distance to (L2). The amount of initial tension is equal to two (2) times the load achieved at (L1) minus the load at (L2). The formula for Initial Tension Simplified is (Pi) = 2P1 - P2.

Initial Tension Graph

Initial Tension Graph

Extension Spring Ends

Standard Machine Hook
Standard Machine Hook
Extended Machine Hook
Extended Machine Hook
Enlarged Machine Hook
Enlarged Machine Hook
Double Cross Center Hook
Double Cross Center Hook
Drawbar Hook
Drawbar Hook
Rectangular Hook
Rectangular Hook
Reduced End Swivel Hook
Reduced End Swivel Hook
Tear Drop Shaped Hook
Tear Drop Shaped Hook
Threaded End
Threaded End

Extension Spring Diagrams

Stresses on an extension spring’s ends are often higher than the stress on a spring’s body. A minimum bend radius of 1-1/2 times the wire diameter is recommended for extension springs. Designs should ensure the end’s torsional stress does not exceed 40-50% of the tensile strength and the end’s bending stress does not exceed 75% of the tensile strength.

Extension Spring Diagram
Extension Spring Stress Diagram

Below are just a small selection of the extension spring shapes we have produced, including:

  • Auger Spring
  • Bungee Cord End
  • Door Return Springs
  • Drawbar Extension Springs
  • Cross Center Loop Ends
  • Expanded Hook Ends
  • Reduced Hook Ends
  • Standard Hook Ends
  • Swivel Ends
  • Tear-Drop Shaped Hook Ends
  • Threaded Insert
  • Garter Springs
  • Handle Springs
  • Jumper Springs
  • Rectangular Ends
  • Stove/Oven Springs
  • Tie Down Springs
  • V-Hook
spring gallery

Extension Spring Manufacturer Gallery

As a custom extension spring manufacturer, Newcomb Spring can produce a wide variety of extension spring (tension spring) shapes, sizes and designs. Using material sizes from .007 to .625 inches in wire diameter, all Newcomb extension springs are precision manufactured to meet even the strictest order requirements.

We produce extension springs with varying body lengths, widths, and a virtually unlimited variety of end types. With over a century of spring design and manufacturing experience, we can provide design assistance on your extension spring order, helping lower production costs and review your part's fit and function.