Frequently Asked Questions

1. What is the difference between Closed and Closed Ground ends (for Compression Springs)?
   
   Compression springs can be coiled with many different configurations for the ends. If the space between the last two coils is reduced so that the end of the spring touches the previous coil the ends are said to be closed. If the end of the springs keeps the same pitch (space between the coils) the ends are said to be open. In either case the springs can be finished with a grinding procedure that causes the ends to be flat. When this is done on a closed end spring then the spring is now considered closed & ground.
   
   The most common type of compression spring for industrial use is closed and ground. Grinding the ends becomes more beneficial as the wire diameter increases, to ensure a flatter surface for the ends.
   
   
2. What is the free length of a spring?
   
   For a compression spring this is measured from one end of the spring to the other when no load is applied. For an extension spring this is measured from inside diameter of each hook before any load is applied.
   
   
3. What is solid height (for a compression spring)?
   
   The solid height is the measurement of the spring when it is completely compressed. At this point all the coils are now touching and there is no more space for the spring to compress further. Depending on the spring design and the requirements of the spring, not all springs can safely be compressed to solid.
   
   If the spring is overstressed at solid, the spring will begin to take a set. When this spring is returned to its uncompressed state it will be shorter than the it was originally. It is important to make sure the design of each spring allows it to be compressed to the desired height safely, and without added stress, to ensure proper life of the spring.
   
   
4. What is initial tension (extension spring)?
   
   Extensions springs require a certain amount of force to be applied before any deflection is realized. Deflection is the point where the coils start to separate and the spring extends. Once the initial tension is reached and the spring will start to expand at the predetermined rate of the spring.
   
   For example if a spring has an initial tension of 20 lbs. and the spring rate is 15 lbs./in.. It will take 35 lbs of force to pull the spring apart one inch, 20 lbs. of initial tension and 15 lbs of spring rate. To expand it to two inches it will take 50 lbs of force, 20 lbs of initial tension and 15 lbs for each inch. And so on and so on.
   
   
5. How long will a spring last?
   
   A correctly designed spring, without any extraordinary stress will last indefinitely. Designing a spring based on its operating environment is necessary to increase the life of the spring. If the spring is in a corrosive environment, or under extreme temperatures, the proper material must be used in the design of the spring. Using a stainless steel material, or putting a protective finish on the spring according to the elements involved will increase the life cycle of the spring.
   
   
6. How do I know if a spring is left hand or right hand wound?
   
   The best way to determine the direction of the spring is to use your right index finger and lay it over the spring. If the end of the spring starts at the tip of your right index finger and proceed to wrap towards you palm this is considered a right hand wound spring. Conversely, a left hand wound spring would start at the tip of your left index finger and wrap towards your left palm.
   
   
7. Does it matter if a torsion spring is left or right hand wound?
   
   Yes. A torsion spring should be coiled so that the spring would wind up as a load is applied. If the spring unwinds as a load is applied it should probably be coiled in the opposite direction.
   
   
8. What is the proper deflection of a spring?
   
   Deflection refers to the distance a compression spring is compressed, the distance an extension spring is extended, and the distance a torsion spring is rotated. Every spring is designed with a certain amount of safe deflection. If a compression spring is compressed more than its safe deflection it will begin to take a set, and not come back to its original height. If an extension spring is extended beyond its safe deflection the spring will begin to increase in length as it is returned to its original position. The same is the case with a torsion spring, if it is wound beyond its safe deflection it will take a set and not unwind to its original starting position.