Below are some common terms used when referring to units of measure and and other features of spring manufacturing and use.
Glossary of Spring Terms
AC | Active coils. TC – 2 (in most cases) |
Close Ends | The end of the wire coil on a compression spring where it touches the next coil. |
Closed and Ground Ends | Where the end of the wire coil touches the next coil and is ground flat so as to sit flat on a compression spring. |
Compression Spring | An open-coiled spring that offers resistance when compressed. |
Extension Spring | A spring that absorbs and stores energy while offering resistance to being pulled. |
FL | Length of a compression spring. |
Hydrogen Embrittlement | Occurs during the process of plating the spring and may cause it to fail. |
ID | Inside diameter. OD – (2 x wire size) |
Initial Tension | Force that holds the coils tightly together. |
Inside Hook Length | Length from the inside of the hooks or loops. |
Load | Force applied to a spring that enables it to move. |
OAL | Length of an extension spring from end to end. |
OD | Outside diameter. ID + (2 x wire size) |
Pitch | Distance from the center of one wire to the center of the next wire. |
Plain End | Where the pitch remains the same throughout the spring including the end coils on a compression spring. |
Solid Height | Height of a spring when fully compressed. |
Spring Index | The ratio of coil diameter to wire diameter. |
Spring Rate | Amount of lbs it takes a spring to move 1 inch. |
Stress Relieve | Heating a spring at a lower temperature to remove stress from coiling. |
TC | Total number of coils in a spring. |
Torsion Spring | A spring that is rotated offering resistance to externally applied torque. Ends can vary in length and be bent. |