Compression Springs

Helical Compression Springs Made from Spring Steel and Stainless Steel

Helical compression springs are cylindrical springs that are loaded by axial compression. They store mechanical energy while being compressed and release it when the load is removed. Typical applications include return mechanisms, valves, locking systems, electrical contacts, clamping elements and actuating mechanisms.

The Febrotec standard range includes more than 7,500 variants made from spring steel 1.1200 and stainless steel 1.4310. Available wire diameters range from 0.1 to 6.3 mm, with numerous combinations of diameter, length, spring force and spring rate. Many versions are available directly from stock. Different dimensions, forces, materials and surface finishes can be supplied as custom-made springs.

How to Select a Suitable Helical Compression Spring

The available installation space, required spring travel and required spring force should be determined before selecting a spring.

1. Determine the available installation space: Define the maximum possible free length and the available diameter. If the spring is guided inside a bore or sleeve, the outside diameter is particularly important. If it is guided over a rod or shaft, the inside diameter must be taken into account.

2. Define the spring travel and required forces: Determine the spring length and required force at the relevant operating points. For a reliable selection, it is helpful to know at least two values, such as the force at the installed length and the force at the fully loaded operating position.

3. Check the type of loading: Springs used in dynamic applications with frequent load cycles must generally be utilised less heavily than springs exposed mainly to static loads. Stroke frequency, preload and lateral guidance also influence service life.

4. Select the material: Spring steel is suitable for many dry standard applications. Stainless steel offers increased corrosion resistance and is suitable for damp environments. Temperature, cleaning agents and aggressive media must be considered separately.

Meaning of the Technical Specifications

The product table contains the most important values for selecting a compression spring:

• Da – outside diameter: maximum external diameter of the spring.

• Di – inside diameter: free diameter inside the spring.

• d – wire diameter: diameter of the spring wire.

• L0 – free length: length of the unloaded spring.

• L1 – test length: specified spring length at which the test force F1 is stated.

• F1 – force at L1: spring force at the specified test length.

• c – spring rate: change in spring force per millimetre of spring travel, stated in N/mm.

• Lc – approximate solid length: spring length when the coils are fully or almost fully in contact.

The test length L1 is not automatically the maximum permissible load position. The solid length Lc is also primarily a geometrical reference value and should not be used as a normal operating position without technical verification.

Spring Force and Spring Rate

For a linear helical compression spring, the change in spring force is calculated from the spring rate and the additional spring travel:

Force change ΔF = spring rate c × spring travel Δs

A spring with a spring rate of 5 N/mm increases its force by 20 N when compressed by an additional 4 mm. For the actual product selection, the stated test force F1 and corresponding test length L1 should also be taken into account.

Materials and Surface Finishes

The standard range of helical compression springs is available in two materials:

• Spring steel 1.1200: an economical solution for dry standard applications. Stock springs are supplied with an oiled surface.

• Stainless steel 1.4310: a corrosion-resistant spring material for many damp and technically demanding environments. Due to cold working, the material may be slightly magnetic. The springs are supplied with a bright finish.

Additional materials such as Inconel, Incoloy, Nimonic, Hastelloy, beryllium copper and phosphor bronze are available on request. Possible surface treatments include electrogalvanising, zinc flake coating, passivation, electropolishing and black oxide coating.

View the Material Overview

Solid Length and Presetting

The solid length is reached when a compression spring is compressed until the coils are fully or almost fully in contact. Repeated or permanent compression to the solid length may result in overloading, permanent deformation and a reduced service life.

During presetting, a spring is compressed in a controlled manner to a defined load position. This can create beneficial residual stresses. At the same time, the free length L0 may decrease slightly. Whether and how a spring is preset depends on its design and intended application.

End Design and Coiling Direction

Depending on the wire diameter and product series, the spring ends are closed or additionally ground. Ground ends improve the seating surface and support more uniform axial force transmission.

In the standard product range, 0C and 0X springs with a wire diameter of 0.50 mm or more and 0D springs with a wire diameter of 1.00 mm or more have closed and ground ends.

The springs in the standard range are generally right-hand coiled. Left-hand coiled or counter-wound versions can be assessed as custom-made springs.

Tolerances

The specified tolerances of EN 15800 apply to the Febrotec 0D and 0X product ranges. The 0C range is manufactured according to a factory standard. The permissible deviations depend on factors including the spring dimensions, wire diameter and the characteristic being toleranced.

For applications with strict requirements regarding diameter, length, spring force or spring rate, the required tolerances should be specified when submitting the enquiry.

Custom-Made Springs and Alternative Spring Designs

If no suitable helical compression spring is available from the standard range, we can manufacture springs according to your technical specifications. For an initial assessment, please provide the following information whenever possible:

• installation length,

• outside or inside diameter,

• required spring travel,

• required spring forces,

• material and environmental conditions,

• intended type of loading,

• required quantity.

A drawing, sample or photograph of the installation situation will help us assess the application.

Where installation space is particularly limited or high forces are required, die springs, conical springs or multi-wave springs may be suitable alternatives.

Request a Custom-Made Helical Compression Spring

Frequently Asked Questions About Helical Compression Springs

Should I Select the Spring by Its Outside or Inside Diameter?

If the spring is guided inside a bore or sleeve, the outside diameter is the decisive value. If the spring is guided over a rod or shaft, the inside diameter must be sufficiently large.

Can a Compression Spring Be Compressed to Its Solid Length?

The solid length should not automatically be used as a permissible operating position. Whether a spring can be compressed close to its solid length must be assessed for the individual spring and type of loading.

Can a Helical Compression Spring Be Shortened?

Shortening a spring changes its free length, number of active coils, spring force and end design. A standard spring should therefore not be shortened without technical verification.

What Can I Do If No Standard Spring Fits?

First use the tolerance filters in the product table. If no suitable stock spring is available, we can assess a custom-made spring or an alternative spring design.

Technical Support

Our technical team will help you select a stock spring and design custom-made helical compression springs.

Please send us the installation dimensions, required forces, spring travel and information about the environmental conditions.

Request Technical Support