How Do You Custom Order Small Extension Springs?

You need a tiny extension spring for your new device, but stock catalogs have nothing that fits. Your project is stalled, waiting for a small part that seems impossible to source.

To custom order a small extension spring, you must provide four critical details: the wire diameter, the outer diameter of the coils, the length between the hooks, and the type of hooks needed. These core specifications allow a manufacturer to accurately produce the spring.

I've seen many innovative product designs get delayed by a simple, tiny spring. The problem is that "small" isn't a specific enough measurement for manufacturing. A spring that's small for an automotive application could be gigantic for a medical device. Getting your custom spring made quickly and correctly depends on providing clear, precise information. Let's break down exactly what a spring maker like me needs to create the perfect part for you.

What Are the Most Critical Dimensions to Provide?

You sent a drawing for a small spring, but the manufacturer is asking for more information. You're not sure which numbers are the most important, causing delays in your project.

The four most important dimensions are wire diameter, ytre diameter, length inside the hooks, and material type. These numbers control the spring's pulling force, how it fits into your assembly, and how long it will last in its working environment.

Tidlig i min karriere, a customer asked for a "small spring that pulls with about one pound of force." This is a very common but difficult request. Without the core dimensions, there are thousands of possible spring designs that could meet that requirement. It's like asking a builder for a "small room" without giving any measurements. We need the blueprint. Providing the wire diameter, coil diameter, and length gives us the exact size and shape. Specifying the material tells us what it's made of. With just these four pieces of information, we can calculate the spring's performance and give an accurate quote.

The Blueprint for Your Spring

These four measurements are the foundation of your custom spring design.

• Tråddiameter (d): This is the thickness of the wire itself. It has the biggest impact on the spring's strength and force.
• Ytre diameter (OD): This is the width of the spring's coil body. It determines if the spring will fit into your assembly.
• Length Inside Hooks (LIH): This is the total length of the spring from the inside of one hook to the inside of the other when it is relaxed.
• Material: The type of wire used (f.eks., Rustfritt stål 302, Music Wire). This affects corrosion resistance, tretthet liv, and cost.

How Do You Specify the Pulling Force You Need?

Your prototype spring is either too weak to do its job or so strong it's bending other parts. You need to control the force, but you don't know how to ask for it.

You can specify the force by providing a "spring rate" or by stating the load it should have at a specific extended length. For eksempel, "The spring needs to provide 5 lbs of force when stretched to 2 inches long."

This is where we move from just the shape of the spring to its actual function. A customer once needed a spring for a small lid. Their first prototype was too strong and made the lid snap shut dangerously. The second was too weak and the lid wouldn't stay closed. The problem was they were only focused on the spring's size. I explained that we needed to define the force. We worked together to determine they needed a spring with 2 Newtons of force at an extended length of 25mm. With that one piece of data, we adjusted the design and the next sample worked perfectly.

Defining the Spring's Job

There are two main ways to tell us how strong the spring needs to be.

• Spring Rate: This is the amount of force required to stretch the spring by a certain distance (f.eks., lbs/inch or N/mm). It defines the spring's stiffness.
• Load at Length: This is a more direct method. You specify a target load at a specific extended length. This is often easier for designers who know the exact force they need in their mechanism.

What Kind of Hook Ends Do Small Springs Need?

The hooks on your small spring keep breaking or slipping off their mounting posts. The standard hooks you've tried are not working for your compact and delicate design.

For små fjærer, hooks must be chosen based on space constraints and the stress they will endure. Common choices include machine hooks for durability and extended hooks for reaching specific connection points. The hook design is just as critical as the spring body.

I remember working on a project for a small electronic device where a standard hook was too bulky. It was touching another component and causing a short circuit. The spring's body was perfect, but the hook made it unusable. The solution was a custom hook[^1] with a very small loop and a specific orientation that kept it clear of the other electronics. For små fjærer, space is everything. You also have to consider the stress. A simple crossover hook might seem fine, but it creates a high-stress point that can break after repeated use. A small machine hook is often a much more reliable choice, even if it costs slightly more to produce.

Choosing the Right Connection

The hook connects your spring to your product, and it must be a perfect fit.

• Hook Type: The shape of the hook is critical for strength and fit. Machine hooks are generally stronger than crossover hooks. Full loops can be used to slide over a post.
• Hook Orientation: The angle of the hooks relative to each other (f.eks., in-line at 0 grader, or at 90 grader) can be specified to make assembly easier.
• Hook Opening: The size of the gap at the end of the hook can be made smaller to prevent it from slipping off.

Konklusjon

To custom order small extension springs, provide precise dimensions, define the required force, and carefully select the hook design. This clarity ensures you get the perfect part for your product.

[^1]: Custom hooks can optimize fit and performance, especially in tight spaces.