Allow Clearance for dynamically-loaded custom extensions springs. When deflected, extension springs do not require central arbors or holes that would prevent buckling. Sudden dynamic loading or unloading may cause the extension spring to vibrate laterally, which may induce additional stresses and result in noise and premature failure. The appropriate clearance can reduce or alleviate these stresses and results.
Static Operating Stress — Because extension spring wire ends are often stretched, distorted or marked during loop-making, the maximum recommended stress of the ends is lower than in the body of the spring.
Tolerance Guidelines — Because some spring manufacturers have different process capabilities that may vary tolerance values, discuss your commercial-free lengths, the angular relationship of ends and load tolerance needs with your manufacturer.
Close tolerances can increase manufacturing costs.