| Active Coils (na) |
Those coils which are free to deflect
under load. |
| 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 ends is ground to provide a flat plane. |
| Close-wound |
Coiled with adjacent coils touching. |
| Coils per Inch |
See Pitch. |
| Deflection (F) |
Motion of spring ends or arms under the application
or removal of an external load (P). |
| 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. |
| Free angle |
Angle between the arms of torsion spring when the
spring is not loaded. |
| Free length (L) |
The overall length of a spring in the unloaded
position.
|
| Helix |
The spiral form (open or closed) of compression,
extension and torsion springs.
|
Hooke's Law |
Load is proportional to displacement. |
| Hooks |
Open loops or ends of extension springs. |
| 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. |
| 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 spring. |
| Initial tension (Pi) |
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 causes a deflection
(F).
|
| Loops |
Coil-like wire shapes at the ends of extension
springs that provide for attachment and force application. |
| Mean coil diameter (D) |
Outside spring diameter (O.D.) minus one wire diameter
(d). |
| 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. |
| 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). |
| Rate (R) |
Change in load per unit deflection, generally given
in pounds per inch. (N/mm) |
| Slenderness ratio |
Ratio of spring length (L) to mean coil diameter
(D). |
| Solid height (H) |
Length of a compression spring when under sufficient
load to bring all coils into contact with adjacent coils. |
| Spring index |
Ratio of mean coil diameter (D) to wire diameter
(d). |
| 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. |
| 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 oz./in., lb./in., lb./ft., or in N/mm. |
| Total number of coils (Nt) |
Number of active coils (Na) plus the coils
forming the ends. |
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