Active Coils Vs. Total Coils and Basics on Spring Coil Counting

active total coils spring

Within the world of spring manufacturing, particularly coil springs, one of the most misunderstood elements out there is counting coils. While totaling up coils is important for a few reasons within spring manufacturing and use formats, this simple process comes with more errors than you might think, both in design and new product development areas.

At J & J Spring Enterprises, we’re happy to explain coil counting basics to you for any of our coil springs, plus provide similar details for drag springs, torsion springs, flat springs and all of our other products. Let’s take a look at both compression and extension springs, and set you straight on coil counts and what they mean for a given spring.

Active Coils vs Total Coils on Compression Springs

The primary sticking point when it comes to compression springs is the difference between active coils and total coils. For a coil to be active, it must be able to either deflect, extend or bend (for torsion springs) as needed. When a compression spring sits on a surface, for instance, it’s able to do this because the end coil has been closed and is touching the adjacent coil, and the final coil is ground to remove part of the material.

But because the end coil sits flat on the table, it is not capable of deflection – this means the coil is inactive. There’s also another inactive coil on the other end. In this case, this compression spring would be viewed as two inactive coils, plus whatever number of active coils exists between these two ends. The same goes for cases where the end coils are not ground.

In other cases, the spring manufacturer will create a higher compression spring where all coils touch each other. This is referred to an “at solid” spring, where two or three coils may touch at the end of the spring. In such situations, all coils touching each other are inactive, not active.

Extension Spring Differences

When counting coils for extension springs, on the other hand, things will be a bit different. Extension spring manufacturers generally figure out the number of active coils required, then two additional coils are added for hooks or loops. One coil on each end of the spring is bent out to create the hook or loop, reducing the active coils on this spring by two. So in essence, the only coils that are considered active on an extension spring are the coils on the helix itself. In cases where an extended hook or loop is needed, the spring is first wound with the proper number of active coils, and then a straight end is added for bending later.

For more on counting coils on your springs, or to learn about any of our spring manufacturing services, speak to the staff at J & J Spring Enterprises today.