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Your Ultimate Guide to Spring Terminology

There’s a wide variety of springs in the manufacturing industry. To help you keep up with all of them, including  be knowledgeable with their benefits, below is a complete guide to spring terminology.

Your Ultimate Guide to Spring Terminology - KB Delta

Good knowledge of spring terminology and definitions used in the spring industry is important, if you must choose the right spring for your application. In this case, you can provide the information required to manufacture a spring and avoid mistaking one component for the other.

A deep understanding of descriptive spring terms is also useful when ordering springs since you’ll be able to develop the precise set of specifics to use. This is most especially useful when you’re trying to address certain issues in your spring that can only be solved using a particular type of spring or element.

It could be coil spring, torsion spring, extension spring, leaf spring, helical spring, compression spring, and lots more, but the same applies.

Now that you know the benefits of spring terminology and definitions, here is an extensive glossary of spring terms to help you begin.

Glossary of Spring Terms

Outlined below is the definition of some spring terms:

1. Active Coils (NA):

Coils that are free to deflect while under load/torque in an extension/torsion spring. They are also coils within the spring and not at the ends of the spring.

2. Angular Relationship of Ends:

The position of the hooks between each other.

3. Baking:

Electroplated springs under heat treatment to release hydrogen embrittlement.

4. Barrel Spring:

A spring with smaller coil diameters toward its end, which gives it a barrel/concave shape. These springs are used to produce linear force in cases where the top and bottom outer diameter are smaller compared to the center outer diameter.

5. Blueing:

Heating until a thin blue film of oxide is formed on ferrous alloys.

6. Buckling:

Bending of compression springs upon compression.

7. Close Wound:

The phenomenon of coiling where adjacent coils touch each other.

8. Decarburization:

The opposite of carburization, and involves the reduction of carbon content on the surface of metals or steel during a high-temperature process.

9. Deflection (x):

Movement of spring ends or arms when an external load is applied or removed.

10. Elastic Limit:

The limit to a spring’s deflection after it has undergone high levels of stress.

11. Free Angle/Position:

The position of a torsional spring’s legs when it is in a free, untorqued state.

12. Free Length:

The length of a compression spring when there is no load applied to it.

13. Frequency:

The rate of vibration of a spring when both ends are grasped/attached.

14. Helical Spring:

Spring with round or circular coils. They are used to store and release energy in a bid to absorb shock.

15. Helix:

Round or circular.

16. Hooke’s Law:

Robert Hooke’s law of physics states that the strain in a spring is proportional to the force applied within the elastic limit of that spring.

17. Hooks:

Ends of extension spring that have been bent out to enable the grasping of objects.

18. Hourglass Spring:

Spring whose coil diameters are larger toward the ends thereby forming an hourglass/convex shape.

19. Hydrogen Embrittlement:

Springs that are brittle as a result of hydrogen absorption in electroplating, which could lead to cracking and failure.

20. Inner Diameter:

Measuring a coil’s interior from side to side.

21. Initial Tension (Fi):

The force between an extension spring’s coils that keeps them together in their free state.

22. Load:

Force applied to a spring.

23. Loops:

Woundings at the end of extension springs to aid in attachment and force application.

24. Mean Coil Diameter:

The outside spring diameter (O.D.) minus one wire diameter.

Your Ultimate Guide to Spring Terminology - KB Delta

25. Modulus of Elasticity in Shear or Torsion:

The coefficient of stiffness for compression and extension springs.

26. Modulus of Elasticity in Tension or Bending:

Coefficient of stiffness for flat or torsion springs.

27. Open Ends, Not Ground:

The end of a compression spring with a constant pitch for each coil.

28. Open and Ground Ends:

A constant pitch of the coils but ends ground.

29. Passivating:

Acid treatment of stainless steel in a bid to eliminate contaminants and replace oxide film to improve its corrosion resistance.

30. Patenting:

Heating of carbon steel above its critical temperature, before cooling slowly to give a fine pearlitic microstructure with good ductility and conducive to drawing.

31. Permanent Set:

Difference between a spring’s original free length and its length after deflection to a certain height and released.

32. Pitch:

The distance between a coil and another in open wound springs.

33. Poisson’s Ratio:

The ratio of strain in the transverse direction to the strain in the longitudinal direction.

34. Rate:

Change in load per unit of deflection, measured in pounds per inch.

34. Remove Set:

Elongating a spring more than its desired free length, and then compressing it to a solid height in a bid to enable the spring to take a set and increase its elasticity.

36. Residual Stress:

Stress-induced by preset, cold working, shot peening, forming, etc.

37. Scragging:

Pressing to solid to remove set.

38. Set:

A change in length caused by deflection beyond the material’s elastic limit.

39. Shot Peen:

Bombardment of the wire surface with small steel shot in a bid to induce compressive stress and improve fatigue life.

40. Slenderness Ratio:

Proportional ratio of compression spring’s free length to mean coil diameter. It determines the ability of the spring to bend during deflection.

41. Solid Height:

Height of a compression spring when it is subjected to sufficient load to bring all the coils into contact with adjacent coils.

41. Spring Index:

Proportional ratio of the mean coil diameter to spring’s wire diameter, which determine its coil’s tightness.

42. Stress Relieve:

Process of low heat-treating to relieve stress on springs.

43. Telescope:

The effect made by conical, convex, or concave springs due to the compression of their coils’ outer diameter into the next coils’ inner diameter.

44. Torque (M):

The action of twisting a torsional spring’s legs and coils under a radial force.

45. Total Number of Coils (N):

The total amount of coils in spring, whether active or inactive.

46. Wahl Factor:

A stress factor that corrects stress in helical springs; effect of direct shear and change in coil curvature.

47. Wire Diameter:

Measurement of the round wire thickness which the spring is made of.

Your Ultimate Guide to Spring Terminology - KB Delta


With this guide to spring terminology, you have an arsenal of words to use when it comes to developing the accurate specifics for your spring. These terms can be used when communicating with other manufacturers in the industry, and ensuring that your spring’s specification is right for its application.

Remember, the right specifications can go a long way to impact on your spring’s quality and lifespan.

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