Most extension springs are fully compressed springs with hooks, eyes or attachments at each end that hook onto machinery. An extension spring is wound tightly to only uncoil when pulled with a certain amount of force, making it ideal to pull parts back into place.

They are mainly constructed using stainless steel, high carbon steel wire, nickle base alloy or brass. Some extension spring manufacturers add finishes to the springs they create, providing some protection from corrosion.

Extension springs have many different uses, from screen door retractors to circuit breakers. Garage door extension springs help get the door back in place once it's opened.

1. In low to medium stress situations, it's possible to use plastic extension springs. This type of spring is corrosion resistant and quieter than metal springs.

2. Using an extension spring with a heavier load than recommended can drastically reduce its lifespan.

3. The most common place for an extension spring to fail is the end, where the hook is. The risk from this can be diminished by creating an extra half-loop before adding the hook.

Action Steps
The best contacts and resources to help you get it done

Find industrial extension spring distributors

Distributors of industrial extension springs usually offer many different extension springs to choose from. They're often sold by outside diameter, wire diameter, free length and load. It's a good idea to let the extension spring manufacturer help you decide what size extension spring you'll need. A representative should be able to help you pick a metal type, maximum load, and more.

I recommend: Check out Stanley Spring and Stamping's selection or get an extension spring from the Penn-Elkco Spring Co..

Purchase extension spring end pieces

Some extension springs come with an end already attached, while others are available separately. The type of end piece you choose depends on on what job you need your extension spring to preform. There are hundreds of different end pieces to pick from. But if you can't find the perfect one from you, most extension spring suppliers will work with you to create the perfect fit for your application.

I recommend: Check out the extension spring end pieces available from the Master Spring & Wire Form Co., or get a custom extension spring hook from the Ajax Wire Specialty Company.

Commission custom extension springs

Custom extension springs are best when you can't find the particular traits you're looking for. Custom extension springs allow you to work with the extension spring supplier to get the exact type of materials, load and size you're looking for, regardless of the manufacturer's stock. You can also have them made to meet your product's demands.

I recommend: Get a custom extension spring from the Diamond Wire Spring Company or buy extension springs from the Hardware Products Company.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  If you're looking to save money, consider using music wire to make your extension spring. It's a cold-drawn wire with uniform strength, and provides a cheap alternative to steel, nickel or brass. While it's not appropriate for the heaviest loads, music wire works well for the vast majority of applications without costing a lot.