Spring Terminology

Coils that are free to deflect under load

Extension and torsion springs, relates to relative end positions of loops and legs respectively.

Process of heating the material so that it becomes ductile and soft.

Heating of electroplated springs to relieve hydrogen embrittlement

Compression spring, lateral displacement due to loading. This effect is a function of slenderness ratio L/D

Generally applies to tension & torsion springs where adjacent coils touch.

End coils of a compression spring are closed and ground flat. See Closed End.

End coils of compression spring are closed by reducing the coil pitch angle until they are square with the spring axis and touch the adjacent coil.

Compression springs, see Solid Height

Number of coils per length, See Pitch

Compression spring, Inactive coils

Distance moved due to an external load

The stress point at which the wire material, if subjected to higher stress, will no longer return to its original shape. Applied to a spring, the maximum stress at a given stress ratio at which material will operate in a given environment for a stated number of cycles without failure.

Torsion spring, angle between legs when not under load.

Compression spring, overall length when not under load.

Ratio of load [N] to deflection [mm].

A process to improve spring relaxation when operating at elevated temperatures.

Wire or bar wound to form a helical coil.

The loss of mechanical energy during loading and unloading whilst operating in the elastic range. Illustrated by the area between deflection curves.

Tension springs, the magnitude of force that is required to separate closely wound coils.

Tension springs, end coil formed into hooks or loops

The average diameter of the mass of spring material

Coefficient of stiffness

Ratio of Stress/Strain

Product of the distance (m) and load (N), from the spring axis to the point of load application. The force component is at 90 degree to the distance line.

Frequency is the ratio of oscillations per unit of time. The natural frequency is the lowest inherent rate of free vibration of a spring oscillating between its own ends

Heat treatment process where carbon steel is heated above its critical temperature followed by a controlled rate of cooling to produce a fine pearlitic microstructure.

Distance from wire centres of adjacent coils in an open-wound spring.

Generally a compression spring where end coils have a constant pitch and not squared

Same as Plain Ends, except wire ends are ground square to the axis

Ratio of change of Load (N) / Deflection (mm)

For a compression spring, it is the permanent reduction in length and is a function of material, stress and temperature. The longer the time period a spring is exposed to higher stresses and higher temperature the greater the relaxation. Springs held at a constant stress relax more than if they are cycled between that stress and a lower stress.

Mechanically induced Stress by processes such set removal, shot-peening, cold working, or forming. It may be beneficial or not, depending on the spring application.

Permanent change of length, height or position after a spring is stressed beyond material’s elastic limit.

Stress at which some arbitrarily chosen amount of set (usually 2%) occurs. Set percentage is the set divided by the deflection which produced it.

Blasting the spring wire material surface with steel or glass beeds to induce compressive stresses to improve fatigue life.

Helical springs, the ratio of spring length to mean diameter L/D.

Compression spring, when loaded to bring all adjacent coils into contact and no further deflection is possible.

Springs formed from flat strip, bar or wire wound into the form of a spiral. Load applied by torque about an axis normal to the plane of the spiral

Ratio of mean diameter to wire diameter.

See Closed and Ground Ends.

See Closed Ends.

Compression spring, angular measurement of the deviation between the axis in free state and a line at right angles to the end planes.

The difference between the operating stresses at minimum and maximum loads.

Ratio of Minimum stress / Maximum stress.

A low temperature heat treatment process to relieve residual stresses produced when the spring is cold formed.

A low temperature heat treatment process to relieve residual stresses produced when the spring is cold formed.

See Moment.

Sum of active coils and dead coils.