Technical Guides
Field notes on choosing springs, taking measurements, diagnosing failures and deciding on materials. The engineering behind our catalogue, in plain language.
What this section covers
Replacing a spring is usually easy; understanding which spring is needed and why the old one failed is the hard part. This section collects the questions that have come back most often from the field since 1978: when a spring should be replaced, why it opens out, how to measure it, and which material belongs where.
You will not find fixed service-life figures, lead times or prices in these articles — those depend on the machine, on how hard it is worked, and on the item ordered. What you will find are the measurable signs to look at when making the decision, and the engineering reasoning behind them.
The order we suggest is this: if something is wrong on the machine, start with the diagnostic articles — when a spring should be replaced, why it opens out, why it breaks. If you are having a new part made, the measurement and material articles will do the job. And if you want to know how a spring actually works, the spring types section covers it in more detail.
The glossary below gathers the terms used throughout these articles in one place. When you place an order or ask for a quotation, these six terms are what establish a common language between us.
Articles
Key terms
The terms used in these articles and in quotation correspondence. All of them are quantities the calculator on our home page also works with.
| Term | What it means |
|---|---|
| Spring rate · k | The force needed to compress or extend the spring by one unit of length (N/mm). On a torsion spring the equivalent is the moment rate (N·mm per degree). This is what people mean by the "stiffness" of a spring. |
| Spring index · C | The ratio of mean diameter to wire diameter (C = Dm/d). It indicates manufacturability: below four the wire is overstrained during coiling, above twelve coiling becomes unstable. |
| Free length · L₀ | The end-to-end length of the spring with no load applied. This is the most honest indicator of fatigue; it shortens before the spring breaks. |
| Solid length · Ls | The length a compression spring takes when fully compressed; about (n+2)·d on a closed-end spring. If the installation gap falls below it, the spring is permanently crushed. |
| Initial tension · F₀ | The force set into the wire of an extension spring during coiling that presses the turns together. The spring does not begin to extend until it is exceeded. |
| Tempering | The heat treatment applied after coiling. It relieves the stress left by coiling and makes the elastic property permanent; skip it and the spring loses length on its first loads. |
If you already have your dimensions
The spring calculator returns rate, solid length and spring index instantly. For compression springs it also computes stress and the safety factor.
Cannot find the spring you need?
We produce to your dimensions in the 0.20–40 mm wire range, with no tooling dependency. A sample, a technical drawing, or simply a photograph of the old spring is enough.
Fill in the quote formOr call us directly: 0850 840 54 17