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
Extension Spring
Extension Spring manufacturing
Custom Spring supplier

Custom Spring Manufacturing Specifications

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

Extension Spring Shapes & Sizes

  • .007 to .625 Inches In Wire Diameter
  • Round Wire
  • Square Wire
  • Rectangular Wire
  • Special Section Wire
Extension Spring Shapes and Sizes

Spring End Types

  • Cross Center Hooks / Cross Loops
  • Draw Bars
  • Extended Machine Hooks
  • Expanded Hooks
  • Standard Machine Hooks
  • Rectangular Ends
  • Reduced 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 Materials

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.

extension spring manufacturing

Extension Spring Ends

Newcomb Spring extension springs can be produced with a variety of ends types, all of which can vary in distance from the spring body. We match all end types to your order specifications, and can change end hook shapes based on customer needs. As one of the industry's leading extension spring manufacturers, we recommend discussing your requirements with a Newcomb sales engineer who can verify manufacturing capabilities and will work to keep your production costs as low as possible.

Standard Machine Hook


Extended Machine Hook


Enlarged Machine Hook


Double Cross Center Hook


Drawbar Hook


Rectangular Hook


Reduced End Swivel Hook


Tear Drop Shaped Hook


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 Length
Extension Spring Stress

Extension Spring Manufacturing Videos


Our spring calculator can assist you with design, spring calculations and stress checks.

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