Skip to content Skip to footer
Mastering and controlling movement


Whether standard couplings with different series made of aluminum or stainless steel or customer-specific developments - we are your strong and experienced Swiss partner.

u-Flex helical couplings are shaft couplings that are manufactured from a single piece of homogeneous material. Their basic shape is a cylindrical body with a helical groove or helix.

This innovative, helical shape allows precise transmission of the rotary movement with high angular accuracy, whereby the elasticity can be precisely calculated. As a flexible shaft connection, the coupling can simultaneously and correctly compensate for various shaft misalignments in three dimensions (angular, radial, axial and oblique misalignment).


Wear-free, flexible, stable – one-piece couplings have many advantages

u-Flex spiral couplings consist of just one piece: this saves space, material and costs. As spiral couplings have no additional moving parts, they are completely wear-free. They also score points for their high dynamic stability and vibration-free, smooth-running bearing loads, even with large displacements.

u-Flex couplings can be used in a variety of ways

Whether measurement and control technology, medicine, aviation, aerospace or mechanical engineering – they always meet the highest design and purchasing requirements. u-Flex impresses with precision, reliability and adaptability, the products meet the highest international standards in terms of design, material and manufacturing technology.


Our know-how - your benefits

Customers who rely on our expertise and experience benefit from several advantages at once. Functional integration (e.g. of coupling/pinion) increases both the service life and safety of components. At the same time, the overall costs resulting from unit costs, assembly and procurement, among other things, can be optimized.

Reduction in total costs

You need fewer components for a function - which means shorter assembly times and minimized procurement costs.

High Security

A single component means clear interfaces. We are also your contact for several functions. This in turn means high system reliability and a high quality standard.

Low storage and administration costs

Thanks to the one-piece couplings from u-Flex, customers need fewer components in stock. This reduces the number of orders and suppliers.

Reduced development effort

On request, we can create design proposals for our customers free of charge. You too can benefit from our expertise and our innovative calculation software.


Aluminium alloys (3.4365) with an anodized surface or corrosion-resistant chrome-nickel steel (1.4542) are used for the standard production of u-Flex spiral couplings.

The material for customized spiral couplings, on the other hand, can be freely selected, as can the connections. The only condition: The desired material must be machinable.

Customized couplings

Customized, innovative solutions are our great strength. Thanks to our extensive know-how and many years of experience, we are able to realize even the smallest couplings for micro devices, for example for implants.

The following parameters can be determined individually:

Helical bar thickness

If the helix pitch changes, the torque, torsional stiffness and axial movement are also influenced by the change in helix thickness.


The material is freely selectable as long as it can be machined.

Bore diameter

Different bore diameters – with the same helix design and the same outside diameter – change the torque, the torsional stiffness and the spring effect.

Length of the helix

Constant torque even when the helix length is changed – all other properties vary depending on the design.

Number of coils

  • Single helix – standard version
  • Two-start helix – start offset by 180
  • Three-start helix – start offset by 120

The use of multi-start helixes increases torque, torsional rigidity and concentricity. However, the possibility of compensating for misalignment is reduced compared to the single-start helix.

Technical basics

the advantages of the u-Flex spiral coupling

u-Flex one-piece couplings can be used in a wide variety of applications. Typical of this Swiss precision is the exact transmission of the rotary movement with high angular accuracy. As a flexible shaft connection, this coupling can simultaneously compensate for various shaft misalignments such as angular, radial, axial and angular misalignment.

Ideal torque capacity

Dynamic loads, vibrations, shocks, additional misalignments and other factors influence the transmittable torque. We calculate the permissible coupling torque based on the technical material data. If all operating conditions are known and do not deviate from the catalog specifications, a spiral coupling is designed for an almost infinite service life in terms of torque transmission.

Individual speeds

Another advantage of the u-Flex coupling is its adaptability to low and high speeds: Over its entire length, it transmits movement evenly in a continuous spiral line. The torsional load tends to wind the coupling towards the axis – this reduces vibration movements that normally occur with rotating parts.

High speeds

High speed range, reversing operation or very high cycle rates with spiral couplings? Low mass moments of inertia make this possible. Our standard spiral couplings are designed for speeds up to max. 10,000 rpm, but couplings have been developed for use up to 50,000 rpm.

Axial compensation

Axial play can either be desired in a specific system or arise due to various individual part tolerances during assembly, temperature changes or torsion, etc. We are happy to calculate the required axial misalignment for our customers and produce the coupling accordingly.

Gentle bearing load

In addition to torques and forces, the coupling has an influence on the bearing load, whereby changing forces in particular can cause damage to bearing points or driven elements. The spring constant of the u-Flex spiral couplings is the same at all points during rotation – this ensures a constant radial bearing load at both low and high speeds.

Configurable torsional rigidity

Our tables provide information on the torsional rigidity of standard couplings. However, it can be adapted for our customers, taking into account the technical specifications. However, every shaft connection has a certain torsional elasticity above a certain torque.

Constant speed

Minimal manufacturing tolerances guarantee precise operation at the same angular speed on the input and output side. The angular synchronization of the connected shafts always remains constant, regardless of the misalignment. One advantage of the one-piece design of u-Flex: The coupling is backlash-free, there is no torsional backlash.

Vibration damping

The helical, flexible coupling profile reduces unwanted torsional vibrations in a rotating system. u-Flex spiral couplings operate quietly and do not generate any natural vibrations themselves.

Variety of types

u-Flex couplings are available in two different versions.

Couplings with through bore

Coupling with rear rotation
– Inner diameter is larger than shaft diameter.
– Shaft ends could touch each other if they are installed too deep in the coupling (must be avoided)
Offset arrangement
– Inner diameter is smaller than large shaft diameter, but larger than small shaft diameter.
– Shafts could touch each other (must be avoided)
Limited shaft length
– Inner diameter and both shaft diameters are the same size.
– Shaft length must be limited to the length of the coupling hub.
– Coupling can be installed or removed by sliding it onto a shaft.
Stepped shaft diameter
– Inner diameter is smaller than shaft diameter.
– The shafts do not touch each other.
– Advantage: high torsional rigidity with small couplings as the helical cross-section can be maximized.

Blind holes or non-through holes

Compared to other designs, this version transmits higher torques and higher torsional rigidity with a smaller outer diameter and shorter length.
However, this coupling is axially rigid and can only compensate for angular misalignments.


Spiral couplings documentation