Screw lock

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NORD-LOCK® Bolt securing system

It is a locking element that complies with DIN 25 201. It locks screwed connections by application of preload-force instead of friction and is thus superior to conventional screw locks.



On the inside, the lock washers have cam faces while on the outside they have radial ribs. The form of the cam faces is chosen so that the cam angle "α" is always larger than thread pitch "β". The pre-assembled washers are instaleld in pairs, cam face to cam face.



If the screw or nut is tightened, the radial ribs of NORD-LOCK® washers form-closedly emboss in the counter-surface. The pair of washers sits tightly in its position and movements are only possible between the cam faces. In case of even the most slight turning in loosening direction, the preload-force is increased due to the wedge effect of the cams. Thus, the screw locks itself. NORD-LOCK® offers reliable screw locks, even for extreme vibration or dynamic loads. Due to the hardness of the washers, they can as well be used for high-strength screws up to property class 12.9.

Your benefits


The NORD-LOCK® screw-locking system takes advantage of the different angle relations between the cam faces and the screw thread for an effective locking of screwed connections in critical applications.

This provides the following benefits:

  • Maximum safety up to screw quality 12.9
  • Reliable screw-locking even under extreme vibration and dynamic loads
  • Easy assembly and removal, reusable
  • Locking function for high and low preload-forces
  • Same operating temperature range as screw / nut
  • Gentle to surface
  • Wide range of dimensions and different materials
  • Chrome-free (VI)

Screw locks

More about this topic: See Böllhoff News no. 27!

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NORD-LOCK® functional principle


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