These are springs which absorb and store energy by offering resistance to a pulling force. The variety of ends that can be used is limited only by the imagination and may include threaded inserts, reduced/expanded loops on the side/center of the spring, hooks at varying positions/distances from the spring body, and different shapes such as rectangular or teardrop-shaped. The most common are the full and crossover hooks that are made with standard tooling and minimize cost. Most extension spring failures occur in the area of the end. To maximize the life of the spring, the path of the wire should be smooth and gradual as it flows into the end. Stress should be held to a minimum, with a minimum bend radius of 1.5 times the wire diameter recommended.
