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How to Properly Measure Extension Springs (and how they work)

It’s important to determine how to properly measure extension springs and understand how they work in order to get the most out of their uses. Read below for details.

How to Properly Measure Extension Springs - KB Delta

There’s an easy way to measure extension springs properly to get the most essential details.

If you’re able to get the right measurement, you would’ve completed the most significant step of determining if the spring is the right fit for your application.

That being said, the goal is to have the right extension spring suited for the job, which begins with measuring the spring’s dimension.

But first…


How Do Extension Springs Work?

Extension springs have been adopted in a wide variety of applications of late. These are springs whose close-wound design opposes the extension that is between mechanisms.

Extension springs offer a return force to components, and these are components that stretch in an actuated position.

Also, these springs have different ends that include teardrop-shaped ends, threaded inserts, reduced eyes, extended twist loops, hooks, expanded eyes, crossover center loops, and rectangular ends.

What’s more, the ends of an extension spring are connected between two mechanisms. The hooks and loops of this spring allow it to absorb energy, and these components are used to send return force to mechanisms connected to the spring.

It’s also worth noting that springs that are tightly wound are positioned in the no-load region. And the application of more stress on the end hooks reduces the performance of the spring.


How to Measure an Extension Spring

Here are the simple steps on how to measure an extension spring:

Have the Right Tools

The first step to measure an extension spring is to be armed with the appropriate tools. The most important tools include micrometer, dial calipers, and ruler.

And if you’re handling a large spring, you may want to use a tape measure instead of the ruler.

Once you have these tools in place, there’s the proper instruction you can fall back on to define the dimension of your spring.

Measure the Wire’s Diameter

The wire diameter of the extension spring needs to be measured at two different locations.

This measurement can be made possible with the use of a micrometer, after which the average is calculated. A measurement of this kind will enable precise readings to be taken, and at the same time provide an accurate ordering.

Measure the Outside Diameter

A measurement of the outside diameter needs to be taken. This measurement is carried out at the center of the spring given that the end coils may run large.

Measure the Body Length

An extension spring’s body is known as the coiled portion. This portion excludes the hooks and loops.

Accordingly, the length of the spring’s body can be taken by using calipers or micrometer for small springs.

Larger springs can be measured using a ruler.

Measure All the Length of the Spring

The overall length of the spring can be taken. This measurement defines the length that is over the top of the ends.


How to Properly Measure Extension Springs - KB Delta


Common Extension Spring Types & Designs

There are different hook ends and even loop ends configurations for extension springs and each configuration is best suited for the function the spring will perform.

Nonetheless, it is important to make modifications to the length of the hook as well as the distance of the body. This will create a modification that will allow the spring to be used for the specialized purpose it is meant for.

Over and above that, there are drawbar extension springs and constant force extension springs.

The former are pitched extension springs and their load are attached to the far ends of the spring. It is also connected via the center of the spring’s loop with a metal.

The constant force extension springs, on the other hand, are created as a result of prestressed, flat metal stripping.

They take the form of a tight coil whose deflection causes the spring to straighten and lengthen in a straight line.


Common Applications of Extension Springs

Extension springs have a wide range of applications and some of these are:

  • Toys
  • Carburetors
  • Trampolines
  • Car interiors
  • Car exteriors
  • Vise-grip pliers
  • Washing devices
  • Farm machinery
  • Garage door assemblies


Custom Extension Springs

It is also possible to design custom spring with different capabilities to fit the right requirement.

These springs can have different ends including German hooks, twist, side loops, cross center, flat stock hooks, and extended hooks.

Moreover, they can be made from a range of materials such as stainless steel, hard drawn, music wire, brass, and so much more.


Production of Extension Springs

Extension springs are metal given that their material is very stiff.

Asides from the use of spring steel, hard drawn steel, music wire, to create these springs, there are other materials that may be used in creating these springs in custom applications.

There are extension springs with a pitch between the coils, and they could make it difficult to spot the initial torsion.

Accordingly, manufacturers often fall back on design units for these springs, in imperial and metric standards.


Spring Safety

Extension springs may fail at some point, and if it does, this failure may pose grave dangers compared to other springs.

For instance, a compression spring that has the same size and material of the extension spring, the latter would pose the safe working stresses of the extension spring at ¾ of the load weight.

In the same vein, the extension spring may be in a safe working load, however, the end attachment of the spring may be weaker. It may be weaker than the spring coil as well as the stress point focused on a certain surface area.

If that happens, the spring may end to warp or break due to the stress.



Knowing how to properly measure an extension spring enables you to design or choose a spring that is fit for your application.

If you can get these springs right, then it’ll reduce the potential of your entire unit failing at some point. The performance of the unit will last for a long time, instead of needing regular fixes.

Accordingly, use the tips outlined above to determine how best to measure your extension spring. You also get to know how these springs work and their application.


How to Properly Measure Extension Springs - KB Delta

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