There are two main reasons why bolted joints fail: spontaneous bolt loosening and slackening. Traditionally, application design has involved trying to figure out which will have the biggest effect on the joint and choosing a solution to handle that one problem. It is a difficult compromise to make, especially when both could cause application failure.
Now, you can count on one solution to meet all your bolt securing needs. Introducing the new Nord-Lock X-series washers — for bolt security without compromise.
Utilizing a unique multifunctional design, Nord-Lock X-series washers offer the highest security against both spontaneous bolt loosening and slackening.
Upon tightening the fastener, the washers flatten and the serrations engage the contact surfaces. Since the cam angle (α) is greater than the thread pitch (β), the wedge-locking effect will prevent any rotation of the fastener. Directly after tightening, the joint settles and the fastener sinks into the surface material. The washers immediately deflect and the spring effect (Fs) counteracts the slackening movement of the bolt, thereby preventing loss of preload on the joint.
These multiple functions continuously act on the bolted joint to maintain preload and prevent spontaneous bolt loosening — serving as an effective solution for vibration, dynamic loads, settlement and relaxation.
Below you find a selection of advantages with Nord-Lock multifunctional wedge-locking solution.
The Junker test, according to DIN 65151, is considered the most severe vibration test for bolt connections. The test exposes the joint to transverse movements underneath the bolted head/nut, while continuously measuring the clamping force.
The Junker test shows that Nord-Lock’s wedge-locking function safely secures the bolted connection, which is verified through the clear increase in tension during untightening. The Nord-Lock X-series kept the highest initial tension thanks to its additional spring effect.
Would you like to learn more about the performance of Nord-Lock X-series washers? Contact your nearest representative through Contact us.
To see how different products function in various circumstances, we can look at the evolution of preload in a bolted joint over time. The graph below illustrates the performance of traditional bolt securing products with composite materials. The diagram shows two phases: a static phase in which settlement is measured (over the period of 4 hours) and a dynamic phase when vibration is added (measured in 30 seconds). Compare how each of the solutions counteracts slackening and handles vibration.
Problems start as soon as the preload falls outside the functional range. If the preload is too high, yielding occurs. If it is too low, there is separation or sliding between the parts. Only Nord-Lock multifunctional wedge-locking solution keeps you within the optimal limits.