Extension Spring

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 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.

Extension Spring Initial Tension GraphNote 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 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. View our Extension Spring Gallery.

Extension Spring
Machine End
Extension Spring
Machine End
Extension Spring
Expanded Machine End
Extension Spring
Double Cross Center Loop
Extension Spring
Drawbar Hooks
standard-machine-end extended-machine-end expanded-machine-end double-cross-center-loop drawbar-hook
Extension Spring
Rectangular End
Extension Spring
Reduced End Swivel Hook
Extension Spring
Tear Drop Shaped End
Extension Spring
Threaded End
Extension Spring
V-Hook End
rectangular-end reduced-end-swivel-hook tear-drop-shaped-end threaded-end v-hook-end

Extension Spring Diagrams

Spring Stresses

Stresses on an extension spring’s ends are often higher then 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 stress diagram

Extension Spring Stresses




View Extension Spring Videos

Small Extension Springs

Extension Spring Order Information

As with all Newcomb Spring-produced parts, we can custom manufacture any extension spring to fit your needs. As a trusted extension spring manufacturer, we have offered great prices, high quality and total customer satisfaction for more than a century.

To experience the Newcomb Spring difference for yourself, contact us today, or request a extension spring manufacturing quote online.

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  •   770-981-2803   •  kando@newcombspring.com  •   © Newcomb Spring Corp.