Extension Springs

From a screen door retractor to a circuit breaker, extension springs are designed to absorb and store energy by creating a resistance to a pulling force. All coils are active in these springs, and it is the initial tension that holds the coils together tightly. Our production capabilities for these components meet almost any client need, from a standard cross center hook to a special purpose extension spring such as a stove spring, used on oven doors, with extended hook ends.

Newcomb Spring-produced extension spring ends include:

- cross center hooks / cross loops - extended machine hooks - standard machine hooks - reduced ends with swivel hooks - threaded inserts

- draw bars - expanded hooks - rectangular ends - teardrop-shaped ends - v-hooks

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All spring ends can all be produced to vary in distance from the spring body. As well, end hook shapes are based on the needs of our customer.

Newcomb Spring offers state-of-the-art production capabilities for the entire manufacturing process. While extension springs are most often produced using round wire because it is the most adaptable to standard coiler tooling, we are capable of producing parts out of:

- round wire - square wire

- rectangular wire - special section wire

Our material size range is .005-inches to .468 inches.

Most extension springs are wound with initial tension. This is an internal force that holds the 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 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.

Initial Tension (P₁) is determined by extending the spring to a given length (L₁) insuring coil separation. The spring is then 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 (P_i) = 2P₁ - P₂.

Our nine ISO-certified manufacturing facilities are ready to offer design assistance, custom-package your spring and wire form part and ensure the springs we produce are 100% compliant to your specifications. Though we can manufacture coil springs, wire forms and stamped parts using virtually any material, the standard materials we use in the spring manufacturing process are:

- spring steel - high carbon steel - low carbon steel - nickel plated carbon steel - stainless alloys - non-ferrous metals

- elgiloy - hastelloy - monel - inconel - titanium

As with all Newcomb Spring produced parts, we can customize and manufacture any component to fit your needs. We offer great prices, the highest quality and a quick turnaround and have provided customers with total satisfaction for over 100 years. Contact us today, or submit a quote request online, and experience the Newcomb Spring difference for yourself.

Click here to request an extension spring manufacturing quote.

Newcomb Spring is a founding member of the Spring Manufacturer's Institute. Some content here has been used with permission of the SMI.