Screw locking

Nord-Lock

For securing threaded connections, even under high vibrations and strong dynamic loads.

Anti-rotation locking

Nord-Lock secures threaded connections and effectively prevents spontaneous loosening, even under strong vibrations.

Nord-Lock wedge-locking washers are mechanical machine elements. They secure threaded connections under vibration by increasing the preload force rather than by friction, making them superior to conventional screw locks.

Method / principle

Nord-Lock consists of two identical wedge-locking washers, featuring radial cogs on one side, which press positively into the mating surface, and wedged cogs on the other, which increase the preload force under vibration.

Applications

The use of Nord-Lock washer pairs is beneficial wherever there is a risk of a threaded connection working loose. Even under strong vibrations and dynamic loads, Nord-Lock guarantees maximum anti-rotation locking since over 30 years.

Product benefits
  • Optimal locking solution under strong vibrations and dynamic loads
  • Well-established locking system for threaded connections
  • Can be used with screws/nuts of all property classes (up to 12.9)
  • Simple to detach and reusable with no performance loss
  • Reliable locking element

Product benefits

There are many good reasons for using our products.

Strength and options.
Point by point.

Optimum locking solution

No loss of clamping force, even under vibration and dynamic loads

Highly effective

Maximum safety is achieved, even with low preload forces.

Application-focussed

Since the locking effect relies on preload force rather than friction, anti-rotation locking is guaranteed on both dry and lubricated surfaces.

Environmentally friendly and corrosion-resistant

The Nord-Lock screw locking system is a reusable system available in a variety of materials and coatings, for maximum adaptability to your applications.

Easy to assemble

Quick and easy assembly/disassembly with standard tools – no retightening required.

Tried and tested

The Nord-Lock screw locking system is officially approved and proven in use – in construction and the rail industry among other sectors.

Detailed description

 

Operating principle

The wedge-locking washers consist of wedge surfaces on the inside and radial ribs on the outside. The shape of the wedge surfaces is chosen to ensure that the angle α is always greater than the thread pitch β. The washers, which are bonded in pairs, are inserted so that the inner wedge surfaces rest on top of one another.

When the screw/nut is tightened, the radial ribs of the Nord-Lock washer press positively into the mating surface. The washer pair is firmly seated in position and movement is only possible between the wedge surfaces. Even the smallest rotation in the unscrewing direction results in an increase in the clamping force due to the wedge effect – so the screw locks itself.

Nord-Lock screw locking system
 

Installation

Nord-Lock wedge-locking washers can be used with screws of all property classes, up to and including 12.9. Nord-Lock washers can be used for screw locking in threaded holes, countersinks and through holes and with studs. Two pairs of lock washers should be used in through holes. In addition, in slotted holes and for soft mating materials we recommend using Nord-Lock washers with a large outer diameter.
Important: Nord-Lock must not be used on unsecured accompanying washers.

Installation examples – Nord-Lock wedge-locking washers can be used with screws of all property classes.

Installation examples

1) Screws in threaded holes
2) Socket head screws in countersinks
3) Through holes (two pairs of washers required)
4) Studs
5) Not for use on unsecured accompanying washer

 

Vibration test with Nord-Lock washers

The Junker vibration test to DIN 65 151 is a proven method of testing and comparing the safety of threaded connections under dynamic loads. Under loading of the threaded connection transversely to the screw axis, the preload force is continuously measured and recorded with a load cell.

The diagram below shows the high anti-rotation locking capacity of the washers. Screws without an adequate locking element demonstrate a clear loss of clamping force in the connection with increasing load changes. These locking elements have no locking effect under vibration. By contrast, with Nord-Lock washers the preload force remains constant over the entire load period. There is only a slight loss of preload force between the contact surfaces and the thread. The wedge-locking effect is demonstrated by a marked rise in preload force during the loosening process.

Test parameters

  • Screw: M 8 (8.8)
  • Preload: 16.5 kN
  • Clamping length: 25 mm
  • Amplitude: ± 0.3 mm
  • Frequency: 40 Hz
Nord-Lock® screw locking system – Junker vibration test as per DIN 65 151 – Setup

Junker vibration test as per DIN 65 151

Setup

 
Test certificate for the Nord-Lock® screw locking system

Junker vibration test as per DIN 65 151 (M 8 screw (8.8) with 25 mm clamping length)

Red = standard M 8 nut with Nord-Lock at 70% of yield point
Green = standard M 8 nut on threaded fastener, clamping length 50 mm
Yellow = nut with plastic insert (DIN 985)
Pink = spring washer
Blue = standard M 8 nut

Product variants

Every project deserves a tailor-made solution.

Learn more about the product types and find the right variant for your particular application.

Nord-Lock with standard diameter

The standard version is suitable for a wide variety of applications – including countersunk bolts.

More

Nord-Lock with large outer diameter

This version is ideal for slotted holes and soft materials.

More

Downloads

Find out more: related downloads.

If you would like to know more, simply download the relevant brochures.

Title Language Version File Download
Nord-Lock washers
For your critical bolting applications
English 2015/06 383 kB / PDF
English 2015/06 383 kb / PDF

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