Springs are one of the oldest mechanical devices for storing energy. With a wide variety of spring sizes and types available, understanding the application is crucial to ensure the design will meet its intended purpose. Likewise, a spring’s size, shape, and loading requirements will determine its suitability for a particular job, with precise measurements crucial to effective performance and a prolonged lifespan.

measuring a compression spring

How Do You Measure a Compression Spring?

There are many ways to measure springs, from a simple rule to specialised electronic equipment. Established standards equally specify a number of different methods depending on the characteristic to be measured. Any method chosen should be appropriate to the size of the spring and the tolerances applied, not least for very fine or flimsy springs as they may change shape if measured incorrectly.

One of the most common methods for checking the length, diameter and pitch is a calliper. Electronic types can be used to provide an accurate measurement. They can also be used to check the wire diameter; however, a micrometre is more accurate. Accurate measurements are crucial when measuring springs, no matter how big or small, as variations in their physical dimensions will impact the spring rate.

A compression spring manufacturer will need to know the following criteria to manufacture a simple compression spring:

  • Wire diameter
  • Number of coils
  • Diameter of spring (internal or external)
  • Free length of the spring (the actual length when no force is applied)

Understanding the difference between total coils and active coils in compression springs is essential, as the end type of the spring will influence the number of active coils. For example, an active coil deflects when force is applied, so if your spring has closed or double closed ends, in which the end coils don’t have any pitch, then not all coils on the spring are active.

measuring a compression spring

Solid Height

The solid height refers to the height of the compression spring when fully compressed, and the coils can no longer be deflected. Any more force applied to a compression spring already at its solid height would not change the height of the spring unless, of course, so much force was added that the spring was to buckle. Solid height, and the formula used to calculate it, depends on the spring’s end type, which we discussed earlier.

large compression spring being measured

There are a lot of different calculations and measurements that go into making high-quality springs, and a good spring manufacturer will have a thorough understanding of how these measurements impact the performance of the spring and the importance of accuracy. Contact Airedale Springs through our enquiry form if you would like to know more about our spring manufacturing capabilities and how we can help you.