Glossary of Spring Terms

Active Coils

Those active coils which are free to deflect under load.

Air Spring

Spring using the elasticity of air, which is one of the fluid springs.
Angular relationship of ends
The relative position of the plane of the hooks or loops of extension springs to each other.

Arbor

A round, hardened rod or shaft upon which springs are wound., Also called a "mandrel"

Baking

Heating of electroplates springs to relieve hydrogen embrittlement.

Blue

A thin blue film of oxide on ferrous alloys, sometimes used to indicate that the material has been stress relieved.

Buckling

Bowing or lateral deflection of compression springs when compressed, related to the slenderness ratio (L/D)

C-Type Eccentric Retaining Ring

Eccentric retaining ring shaped like leter "C", including two types: for one-shaft-use and for in-bore-use.

C-Type Concentric Retaining Ring

Concentric retaining ring shaped like leter "C", including two types: for one-shaft-use and for in-bore-use.

Ceramic Spring

Spring made of ceramics (sintered materials mainly comprising aluminum oxide and the like) as called by its material.

Circlip

Generic term for circular springs, such as C-type retaining ring.

Closed Ends

Ends of compression springs, where pitch of the end coils is reduced so that the end coils touch.

Closed and ground ends

As with closed ends, except that the end is ground to provide a flat plane.

Closed length

See solid height

 

Close-wound

Coiled with adjacent coils touching

Coils per inch

See pitch

Cold Formed Spring

Spring formed in low temperature, such as the cold formed coil compression spring and the cold formed coil extension spring as called by its forming method.

Combination Spring

Combination of Multiple springs to obtain the required characteristics. (Springs may be combined in a serial or parallel way. A combination spring comprising two springs is called serial double spring or parallel double spring.)

Composite Resin Spring

Spring made of composite rresin materials, as called by its material.

Compression Spring

Spring subjected mainly to a compressive force, in the narrow sense, helical compression spring.

Constant Force Spring

Spring that indicates constant load or torque despite of the deflection change.

Constant Rate Spring

Spring deflection of which is linear to the load applied.

Deflection (F)

Motion of spring ends or arms under the application or removal of an external load (P)

E-Type Retaining Ring

Retaining ring shaped like letter "E" for on-shaft-use.

Elastic limit

Maximum stress to which a material may be subjected without permanent set.

 

Endurance limit

Maximum stress at which any given material will operate indefinitely without failure for a given minimum stress.

Extension Spring

Spring subjected mainly to an extensive force, in the narrow sense, helical extension spring (tension spring).

Fastener Spring

Various shapes of spring for fastening.

Flat Spring

Various shapes of spring made of thin flat materials, as called by its material.

Fluid Spring

Spring using the elasticity of gas or liquid, as called by its material.

Formed Wire Spring

Various shapes of springs made of wire, as called by its material.

Free Angle

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.

Frequency (natural)

The lowest inherent rate of free vibration of a spring itself (usually in cycles per second) with ends restrained.

Gas Pressure Spring

Spring using the elasticity of inert gas such as Argon or Helium, which is one of the fluid springs.

Gas Spring

Spring using the elasticity of inert gas such as Argon or Helium, which is one of the fluid springs.

Gradient

See Rate (R)

Grip Ring

Retaining ring used for shafts without grooves.

Heat setting

Fixturing a spring at elevated temperature to minimize loss of load at operating temperature.

Helix

The spiral form (open or closed) of compression, extension, and torsion springs.

Hooks

Open loops or ends of extension springs.

Hot Formed Spring

Spring formed in low temperature, such as the cold formed coil compression spring and the cold formed coil extension spring, as called by its forming method.

Hot pressing

The heat setting.

Hydrogen embrittlement

Hydrogen absorbed in electroplating or pickling of carbon steels, tending to make the spring material brittle and susceptible to cracking and failure, particularly under sustained loads.

Hydropneumatic Spring

Spring using the elasticity of gas or liquid, as called by its material.

Hysteresis

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.

Initial Tension (P)

The force that tends to keep the coils of an extension spring closed and which must be overcome before the coils start to open.

Load (P)

The force applied to a spring that caused a deflection (F).

Lock Washer

Generic term for washers for locking using the spring action.

Loops

Coil-like wire shapes at the ends of extension springs that provide for attachment and force application.

 

Magnetic Spring

Spring using the repulsion force and attraction force by magnetism, as called by its type of function.

Mean coil diameter (D)

Outside spring diameter (O.D.) minus one wire diameter (d)

Metallic Spring

Spring made of metallic materials as called by its material.

Modulus in shear or torsion (G)

Coefficient of stiffness for extension and compression springs.

Modulus in tension or bending (E)

Coefficient of stiffness used for torsion and flat springs (Young's Modulus).

Moment (M)

See Torque

Nonferrous Metal Spring

Spring made of nonferrous metal, as called by its material.

Non-linear Spring

Spring the deflection of which is not linear to the load applied.

Non-Metallic Spring

Spring made of non-metallic materials as called by its material.

Open ends, not ground

End of a compression spring with a constant pitch for each coil.

Open ends ground

"Open ends, not ground" followed by an end grinding operation

Passivating

Acid treatment of stainless steel to remove contaminants and improve corrosion resistance.

Permanent set

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".

Pitch (p)

The distance from center to center of the wire in adjacent active coils (recommended practice is to specify number of active coils rather than pitch.

Pneumatic Spring

Spring using the elasticity of air, which is one of the fluid springs.

Preset

See Remove set.

Progressive Rate Spring

Spring the deflection of which is not linear to the load applied.

Rate (R)

Change in load per unit deflection, generally given in pounds per inch.

Remove 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.

Residual stress

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.

Retaining Ring

Circular spring for preventing the axial movement by snapping into the groove formed on the shaft or the hole. (A grip ring is used for grooveless shafts.)

Rubber Spring

Spring using the elasticity of rubbers, as called by its material.

Set

Permanent distortion which occurs when a spring is stressed beyond the elastic limit of the material.

Slenderness ratio

Ratio of spring length (L) to mean coil diameter (D).

Snap Ring

Circular spring for preventing the axial movement by snapping into the groove formed on the shaft or the hole. (A grip ring is used for grooveless shafts.)

Solid height (H)

Length of a compression spring when under sufficient load to bring all coils into contact with adjacent coils.

Spring

Mechanical element designed mainly to unitse by elasticity or distoriion of an object.

Spring index

Ratio of mean coil diameter (D) to wire diameter (d).

Spring Washer

Generic term for washers for locking using the spring action.

Squared and ground ends

See Closed and ground ends.

Squared ends

See Closed ends.

Steel Spring

Spring made of steel materials as called by its material.

Stress range

The difference in operating stresses at minimum and maximum loads.

Stress relieve

To subject springs to low-temperature heat treatment so as to relieve residual stresses.

Shot peening

A cold-wound process in which the material surface is peened to induce compressive stresses and thereby improve fatigue life.

Squareness of ends

Angular deviation between the axis of a compression spring and a normal to the plane of the ends.

Squareness under load

As in Squareness of ends, except with the spring under load.

Torque (M)

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 inch-oz., inch-pounds or in foot-pounds.

Torsion Spring

twisting Spring subjected mainly to a twisting moment, in the narrow, sense, helical torsion spring. (torsion)

Total number of coils (N)

Number of active coils (n) plus the coils forming the ends.

Variable Rate Spring

Spring the deflection of which is not linear to the load applied.

Waved Spring Washer

Spring washer made by turning wire and formed into a waved shape.

Waved Washer

Spring washer made of thin ring plate on which waving is formed. (curved washer)

Wire Forming

Various shapes of springs made of wire, as called by its material.

Wire Spring

Coil spring made of wire.