spring dimensions

There are many measurements for a springs, and one of the most important aspects of spring design is length. The length of a spring affects its performance and which applications and devices it can be used in, but there are many methods that can be used to determine the height of a spring. These methods depend upon how you are referring to its “height.”

The Solid Height of a Spring

The solid height of a spring refers to the height of the spring when it is fully compressed (i.e. when the coils are all touching). In this state, the spring is no longer able to be deflected. If more force is added to the spring, its height will not change (short of adding so much pressure that the spring buckles).

Calculating the solid height of a springs depends on what type of end the spring has (closed, open, double, etc.). Generally, you would multiply the diameter of the wire used by the total number of coils plus one (you add one coil to the total because you are actually counting the sides of wire, not the total number of coils).

Your spring manufacturer will be able to tell you how many coils you need in your springs based on the wire size and solid height specifications of your design.

The Free Length of a Spring

The free length of a spring is the actual length of a spring when no force is being applied to it (it is not being deflected).

You can measure the free length of a spring in a few ways, each of which depends on the type of spring you are working with. For compression springs, you simply multiply the length of the spring wire per coil by the total number of coils. You do the same for extension springs but also add two coils to the active number of coils. To get the free length of a torsion spring, you multiply the length of the spring wire per coil by the total number of coils and add the lengths of the legs.

The Total Number of Coils vs. Active Coils

Another common method of measuring the length of a spring involves counting the total number of coils. While this is a less precise measure when compared to the solid height and free length of a spring, it can be useful when you are trying to get a quick gauge on the size springs you need for an application.

The difference between the total number of spring coils and the total number of active spring number can be summed up in one word: deflection. Active coils are those that can be deflected. They must compress, extend or bend when a force is applied to a spring.

What Are the Measurement of Your Springs?

We will ask for total and active coils as well as the free length of your springs when you request a quote for your order. These measurements are only a small part of the custom spring design process. If you need engineering advice or help with spring measurements (or anything else), don’t hesitate to reach out to our team.