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Frequently asked questions



u-Flex helical couplings are one-piece shaft couplings made from homogeneous materials. Their basic shape is a cylindrical body into which a helical groove, also known as a helix, is incorporated. Such a helical or DNA-shaped structure allows a precise flex zone, which results in precisely calculable elasticity. The advantage of a helical coupling consisting of a single piece is that several functions and individual parts are combined into a single, space-saving unit. Spiral couplings have no additional moving parts and are therefore wear-free. This guarantees high dynamic stability and vibration-free, smooth-running bearing loads – even with large displacements.

For standard couplings, either clamping hubs or stud bolts are available for connecting the connecting shafts. The following connection types are available from u-Flex GmbH for customized production:


  • alternating set screw or clamping connection*
  • Pins, bolts, studs
  • feather key
  • flange
  • threaded pin, threaded hole
  • Conical bore
  • Single or double flattened
  • bore
  • Spline toothing

*The fastening friction generated here is sufficient to transmit the required torque; an additional feather key is not necessary. However, on request or in special cases, we can also supply a clamp connection with a feather key.

The connections can be freely selected for specific versions. The material specifications are also freely selectable. The only requirement is that you must be able to machine the material.

u-Flex spiral couplings can be used in a wide range of areas, namely wherever movement needs to be mastered and controlled. Whether in valve technology, medicine, aviation, aerospace or mechanical engineering, u-Flex products impress with their precision and durability.

As long as the clutches are used within the specified torque range, they are torsionally stiff.


Angular misalignment occurs relatively frequently. With the spiral coupling, it is achieved by the inner webs closing and the outer ones expanding. With sufficient space between the helical groove, misalignments of up to 20° can be achieved thanks to u-Flex.

Yes, a coupling system must meet high technical requirements in order to be able to compensate for radial misalignment. If the misalignments are not compensated, the resulting lateral forces will damage the bearing points. The helical principle offers an optimum solution – the maximum permissible values in the standard catalog range are ± 0.8 mm. Customer-specific applications also allow higher values.

Yes, a u-Flex spiral coupling can also do this. In this case, the drive shafts do not have a common plane, so a spiral coupling can also compensate for this three-dimensional displacement. Prerequisite: a relatively long helix.

Thanks to low mass moments of inertia, it is possible for spiral couplings to work in a wide speed range, in reversing operation and at very high cycle speeds. Our standard spiral couplings are designed for speeds up to max. 10,000 rpm, but 50,000 rpm have also been achieved. Please contact our technical department for your specific application. We will be happy to provide you with information on what is possible.

In addition to materials (aluminum and stainless steel), a distinction is also made between couplings with a through bore and couplings with blind holes or with a non-through bore.


Precision springs

Thanks to CNC production, maximum customization is possible in terms of dimensions, spring rate and geometry. All machinable materials can be used for the production of springs, so a wide range of materials is available. In addition to conventional materials, lightweight aluminum springs, electrically insulating springs made of plastic or even high-strength titanium springs can also be produced – the choice of materials is therefore almost unlimited.

They are machined from a homogeneous piece. Such springs can be loaded with compressive, tensile and torsional forces as well as bending stresses – and allow an optimally coordinated combination of different spring values. In the case of multi-start springs, the compression or tension is also distributed over several points, which enables a uniform parallel force distribution to the central axis. The more coils a spring has, the more precisely the parallelism is implemented during compression or extension.

This outstanding spring shape enables very precise and constant spring rates of up to ± 0.1 with a repeatability of up to 1 %. It is manufactured from solid material, e.g. from a rod or tube into which a helical groove is cut. This machining process is much better than coiling a spring because it does not create any internal tension, only the natural material tension. This gives the spring a linear spring characteristic curve with high repeat accuracy and fatigue strength.

Where coiled springs fail, whether due to service life, design, material properties or accuracy.


Springs manufactured by chip removal have connections that are reduced to the bare essentials and are reinforced where necessary. Unsupported moments are prevented, for example, by using double pins, cross slots, grooves, mounting flanges, etc. Such integrated connections increase the service life of springs and the installation space can be optimized. Production and assembly costs can often be reduced at the same time.

The spring rate of a conventional coiled spring lies within a tolerance range of +/- 10 %, while machine-produced springs have a tolerance of only +/- 5 %. On customer request, we can also manufacture precision springs with a tolerance of +/- 1 %. A major advantage: Machining manufacturing processes do not generate any internal stresses that first have to be overcome in order to apply force.

The integration of additional functions (e.g. hole, thread, flange or groove) optimizes the installation space and greatly simplifies assemblies, which significantly reduces the assembly effort. Integrated connections (e.g. flange ends, grooves, threaded holes/spigots etc.) also increase the stability of the spring.

A multi-start spring can be used to produce components that can simultaneously absorb compressive, tensile and torsional forces. With multi-start springs, the compression or tension is distributed evenly over several points, resulting in a balanced parallel force distribution. Additional guidance of the spring is not necessary, as no undesirable lateral buckling can occur with multi-start springs.

By optimizing the coil geometry at the start and end areas. The spiral run-out is thickened to increase the strength of the spring in the critical area. The finite element method (FEM) can provide precise information on strength and service life.