How to Measure a Compression Spring
1. Measure the spring wire diameter, preferably to 3 decimal places for accuracy using calipers.
2. Measure the outside diameter of the coils. This might vary slightly from coil to coil, take the larger value measured.
3. Measure the length in its free condition (uncompressed).
4. Count the number of coils. This is also the number of revolutions going from tip-to-tip; count to the closest 1/8th.
5. Note the winding direction of the coils. In most applications this is not important but review surrounding parts whether they require the spring to be in a specific direction.
6. Note the end type of the spring. Compression springs may have the ends ground or not ground, the end coils may be open or closed, or some other configuration that may require a blueprint description.
Open and Ground
Closed Ends, Not Ground
Closed, Squared and Ground
7. Determine the spring wire material type. If the wire is not attracted to a magnet, then it might be a special metal alloy that needs exact identification. If the material is unknown, then take note of any extreme operating conditions such as: very high or low temperatures, presence of corrosive materials or rapid cycling. Learn more about Materials, Finishes and Plating.