We at Master Spring are dedicated to the custom spring and wire form industry. We’ve been making industry-leading custom wire forms and springs since 1945. Our experts are excited to solve any puzzles our clients send our way.
We know that not everyone lives in the world of industrial spring manufacturing—or has our passion for it. If you are wondering what technical spring jargon means, look no further. Below is a handy glossary of terms and definitions.
Still have questions? Let’s talk, or take a look at our technical resources.
Those coils which are free to deflect under load. For compression springs with squared ends, the total number of coils minus two is a good approximation of the number of active coils. For extension springs, the number of active coils is approximately equal to the number of coils in its body. For extension springs with threaded inserts or swivel hooks, the number of active coils is less than the total coils in the body. Hooks and loops add to the number of active coils.
The relative position of the plane of the hooks or loops of extension springs to each other
Heating of electroplated springs to relieve hydrogen embrittlement
Bowing or lateral deflection of compression springs when compressed, related to the slenderness ratio (L/D)
Location on compression springs where pitch of the end coils is reduced so that the end coils touch
As with closed ends, except that the end is ground to provide a flat plane
See Solid Height
Coiled with adjacent coils touching
See Pitch
Motion of spring ends or arms under the application or removal of an external load (P)
Maximum stress to which a material may be subjected without permanent set
Maximum stress to which any given material will operate indefinitely without failure for a given minimum stress
Angle between the arms of a torsion spring when the spring is not loaded
The overall length of a spring in the unloaded position
The lowest inherent rate of free vibration of a spring itself (usually in cycles per second) with ends restrained
See Rate (R)
Fixturing a spring at elevated temperature to minimize loss of load at operating temperature
The spiral form (open or closed) of compression, extension, and torsion springs
Load is proportional to displacement
Open loops or ends of extension springs
See Heat setting
Hydrogen absorbed in electroplating or pickling of carbon steels, tends to make the spring material brittle and susceptible to cracking and failure, particularly under sustained loads.
The mechanical energy loss that always occurs under cyclic loading and unloading of a spring, proportional to the area between the loading and unloading load-deflection curves within the elastic range of a spring
The force that tends to keep the coils of an extension spring closed and which must be overcome before the coils start to open
The force applied to a spring that causes a deflection (F)
Coil-like wire shapes at the ends of extension springs that provide for attachment and force application
Outside spring diameter (O.D.) minus one wire diameter (d)
Coefficient of stiffness for extension and compression springs
Coefficient of stiffness used for torsion and flat springs (Young’s Modulus)
Se Torque
End of a compression spring with a constant pitch for each coil
“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 distance from center to center of the wire in adjacent active coils. Recommended practice is to specify the number of active coils rather than pitch.
The ratio of the strain in the transverse direction to the strain in the longitudinal direction
See Remove set
Change in load per unit deflection, generally given in pounds per inch (or in metric, N/mm)
The process of closing to solid height a compression spring which has been coiled longer than the desired finished length, to increase the apparent elastic limit
Stresses 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
Ratio of spring length (L) to mean coil diameter (D)
Length of compression spring when under sufficient load to bring all coils into contact with adjacent coils
Ratio of mean coil diameter (D) to wire diameter (d)
See Closed and ground ends
See Closed ends
Angular deviation between the axis of a compression spring and a normal to the plane of the ends
As in Squareness of ends, except with the spring under load
The difference in operating stresses at minimum and maximum loads
To subject springs to low-temperature heat treatment to relieve residual stresses
A twisting action in torsion springs which tends to produce rotation, equal to the load multiplied by the distance (or moment arm) from the load to the axis of the spring body. Usually expressed in oz * in., lb. * in., lb. * ft., or in N * mm.
Number of active coils (na) plus the coils forming the ends
A factor to correct stress in helical spring’s effects of curvature and direct shear
**Glossary reprinted with permission from the Spring Manufacturers Institute (SMI) Handbook of Spring Design.
Custom Spring Clips for Electronics
An integral part to the functioning of an OEM’s heat sink, this wire form design is a great example of how repeatable production and inspection processes result in near zero defects.
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