Extension Spring Loop Types
Various types of ends are used to attach the extension spring to the source of the force. They include hooks or eyes at varying positions or distances from the body of the spring, reduced and expanded eyes on the side or in the center of the spring, extended loops, threaded inserts and even rectangular or teardrop-shaped ends. By far the most common, are the machine loop and crossover loop. These ends are made with standard tools in one operation and should be specified when possible to minimize cost.
Unlike compression springs, extension springs do not have a solid stop to prevent overloading. Because of this design stress levels are lower for extension springs than for compression. A special type of extension spring called a drawbar spring, has a solid stop and is a type of compression spring with special hooks.