Glossary of Spring Terms

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.

Close-Wound
Coiled with adjacent coils touching.

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

Heat Setting
Fixturing springs at high temperature to minimize loss of load at operating temp.

Hooke's Law
Load is proportional to displacement.

Hooks
Open loops or ends of extension springs.

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 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)

Solid Height (H)
Length of 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 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.

Please contact us for any of your custom spring needs.