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Screw locking


Solid and reliable: U-NUT® self-locking nuts offer high safety under extreme loads.

Image of a U-NUT® self-locking nut.

For permanent joints

U-NUT® self-locking nuts secure metric screw connections – under dynamic loads and minimal preload force

Safety is the priority: U-NUT® self-locking nuts ensure reliable screw connections – even under extreme conditions. The nut locking function is integrated directly in the nut. This means that the possibility of the screw connection loosening is virtually excluded.

Plus factors

Advantages of U-NUT®

  • Optimal security

    U-NUT® nuts are optimally secured: The friction lock on the thread is highly effective and prevents the connection from loosening.

  • Wide range of variants

    U-NUT® self-locking nuts are made to meet the most diverse requirements. They are available in many dimensions and designs.

  • Choice of materials

    Whether steel or stainless steel: We manufacture U-NUT® self-locking nuts in a variety of materials.

  • Reliable

    U-NUT® self-locking nuts are suitable for high rotation speeds and alternating directions of rotation.

  • Process reliable

    Uniform installation torque and reliable reuse of screw-fastenings assure your processes.

Method and principle

Effective and efficient screw-locking

Operating principle

The U-NUT® self-locking nut has an integrated  A2 stainless steel lock ring. This lock ring functions as a spring on the thread flanks during and after assembly and exerts a clamping force of the nut on the thread.
Thus, the resulting friction torque generated in reaction to the pitch and reactive force is greater than the loosening torque that occurs in use. This results in a friction lock that effectively secures the bolted connection, even at high vibration.


The U-NUT® is used wherever failure of the screw connection would be critical or where screw-locking is always required. The versatility of the U-NUT® makes it suitable for either conventional bolted joints in accordance with VDI 2230, or applications with shorter clamping lengths and unclear fastening parameters.

The lock ring guarantees a secure connection capable of passing the NAS 3350 American National Aerospace Standard test.

Sectional view of the U-NUT®
Forces the U-NUT® exerts on the screw

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Find the right solution for your application

U-NUT® product types

There are two types of U‑NUT® self-locking nuts with metric standard thread.

  • U-NUT® self-locking nut

    U-NUT® cap nut and weld nut variants

    In our standard product range the dimension spectrum extends from M4 to M36, in the materials, steel (SS400 and S45C) and stainless steel (S304). Additional dimensions from M3 to M115 are available for your application on request

    Contact us if you are interested in other designs: We also produce the U-NUT® self-locking nuts with cap, flange or in a thin nut design.

  • GU-NUT® self-locking nuts

    The GU-NUT® self-locking nut with the larger lock ring offers an enhanced clamping function.

    Our standard product range covers the dimension spectrum from M8 to M16 for steel (SS400) and stainless steel (S304). We offer other designs and dimensions on request.


The U-NUT® self-locking nuts

U-NUT® self-locking nuts ensure secure screw connections

Information and more


Are you interested in U-NUT® self-locking nuts? Please download further information here.

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Do you want to know more about our products or services? Our team will be happy to advise you.

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