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The following are common mechanical spring definitiona and terms.
Those coils which are free to deflect under load.
Angular relationship of ends
The relative position of the plane of the hooks or loops of extension
spring to each other.
Bowing or lateral deflection of compression springs when compressed,
related to the slenderness ration (L/D).
Ends of compression springs where the 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
Coiled with adjacent coils touching.
Coils per inch
Same as "Pitch"
Motion of the spring ends or arms under the application or removal of
an external load.
Maximum stress to which a material may be subjected without permanent
Maximum stress at which any given material may operate indefinitely
without failure for a given minimum stress.
Angle between the arms of a torsion spring when the spring is not
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.
The mechanical energy loss that always occurs under cyclical loading
and unloading of a spring, proportional to the are 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 coil starts to open.
Coil-like wire shapes at the ends of extension springs that provide for
attachment and force application.
Mean coil diameter
Outside wire diameter minus one wire diameter.
Modulus in shear or torsion
Coefficient of stiffness for extension and compression springs.
Modulus in tension or bending
Coefficient of stiffness used for torsion and flat springs. (Young's
Open ends, not ground
End of a compression spring with a constant pitch for each coil.
Open ends ground
"Opens ends, not ground" followed by an end grinding operation.
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
Changes in load per unit of deflection, generally given in pounds per
The process of closing to a solid height a compression spring which has
been coiled longer than the desired finished length, so as to increase the
Permanent distortion which occurs when a spring is stressed beyond the
elastic limit of the material.
Ratio of spring length to mean coil diameter.
Length of a compression spring when under sufficient load to bring all
coils into contact with adjacent coils.
Ratio of mean coil diameter to wire diameter.
The difference in operating stresses at minimum and maximum loads.
Squareness of ends
Angular deviation between the axis o a compression spring and a normal
to the plane of the other ends.
Squareness under load
As in squareness of ends, except with the spring under load.
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
Total number of coils
Number of active coils plus the coils forming the ends.