Extension Spring Ends

  • Extension Spring Design Resources – Custom Spring End Configurations

Extension springs require a method of attachment to other parts in an assembly. A wide variety of ends have been developed and used to successfully for many years – for example, threaded inserts, swivel hooks, twist loops, side loops, cross-center loops and extended hooks. Loops are attachment ends that have small gaps, while hooks are loops with a large gap. In fact, the variety of ends is almost unlimited. The most common configurations are those that can be formed during the spring making operation. Typical types include twist, cross center, side loops and extended hooks. Many of these configurations are made by bending the last coils of an extension spring to form loops. Most special hooks are formed from straight sections of wire on the so-called “tangent ends” of an extension spring body.

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Extension Spring Standard Machine End

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Extension Spring Standard Machine End

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Extension Spring Standard Machine End

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Extension Spring Double Cross Center Loop

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Extension Spring Drawbar Hooks

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Extension Spring Rectangular End

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Extension Spring Reduced End Swivel Hook

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Extension Spring Tear Drop Shaped End

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Extension Spring Threaded End

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Extension Spring Drawbar Hooks

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Common Extension Springs End Types

Stresses in loops are often higher than in the spring body. This limits spring performance, particularly in cyclic applications. Generous bend radii in loops and reduced end coil diameters are two methods frequently employed to reduce stresses. In a full twist loop, stress reaches a maximum at point A in bending and a maximum in torsion at point B (as shown in the Location of Maximum Bending and Torsion Stresses in Twist Loops Diagram). Stress at these locations is complex, but can be estimated with reasonable accuracy by:

Recommended practice is to make C2 greater than four.

Location of Maximum Bending and Torsion Stresses in Twist Loops.


Content Copyright Spring Manufacturers Institute, Inc.

This information is attributed to, and provided courtesy of, the Spring Manufacturers Institute, Inc. (SMI). Newcomb Spring and SMI provide this as advisory information only, and disclaim any and all liability of any kind for the use, application or adaption of material published on this web site.

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