Glossary of Terms
Below you will find a brief list of vocabulary, phrases and terms commonly associated with the spring and wire form industry. You will find more in-depth information in the technical page of these terms.
Ends of compression springs where pitch of the end coils is reduced so that the end coils touch.
CLOSED & GROUND ENDS
As with closed ends, except that the end is ground to provide a flat plane.
Motion of spring ends or arms under the application or removal of an external load (P).
Angle between the arms of a torsion spring when the spring is not loaded.
FREE LENGTH (L)
The overall length of a spring in the unloaded position.
Open ends or hooks of extension springs.
INITIAL TENSION (PI)
The force that tends to keep the coil of an extension spring closed and which must be overcome before the coils start to open.
MEAN COIL DIAMETER (D)
Outside spring diameter (O.D.) minus one wire diameter (d).
OPEN ENDS, NOT GROUND
Ends of a compression spring with a constant pitch for each coil.
OPEN ENDS GROUND
“Open ends, not ground” followed by an end grinding operation.
Acid treatment of stainless steel to remove contaminants and improve corrosion resistance.
A material that is deflected so far that its elastic properties have been exceeded and it does not return to its original condition upon release of load is said to have taken a “permanent set”.
The process of closing to solid height a compression spring which has been coiled longer than the desired finished length, so as to increase the apparent elastic limit.
Stress induced by set removal, shot peening, cold working,forming or other means. These stresses may or may not be beneficial, depending on the application.
Permanent distortion which occurs when a spring is stressed beyond the elastic limit of the material.
A cold-working process in which the material surface is peened to induce compressive stresses and thereby improve fatigue life.
SOLID HEIGHT (H)
Length of a compression spring when under sufficient load to bring all coils into contact with adjacent coils.
SQUARENESS OF ENDS
Angular deviation between the axis of a compression spring and a normal to the plane to the ends.
The difference in operating stresses at minimum and maximum loads.
To subject spring to low-temperature heat treatment so as to relieve residual stresses.
TOTAL NUMBER OF COILS (NT)
Number of active coils (n) plus the coils forming the ends.
A factor to correct stress in helical springs effects of curvation and direct shear.