Nord-Lock®

Nord-Lock® consists of two identical wedge washers. These have wedges on the inside and radial ribs on the outside. The wedge surfaces of the washers, which are glued together in pairs, lie on top of each other when in use. The shape of the wedge surfaces is such that the angle between the lock washers is greater than the angle of the thread.

When you tighten the bolt or nut, the radial ribs of the Nord-Lock® washer are pressed tightly into the mating surface on the opposite side. The pair of washers stays securely in place. The only possible movement is between the wedge surfaces. The wedge effect increases the clamping force at the slightest unscrewing rotation: the screw locks itself.

The Junker vibration test in accordance with DIN 65 151 is an excellent method for testing and comparing the security of screw connections under dynamic stress. A pressure cell continuously measures and records the pre-tensioning force while the screw connection is subjected to stress at right angles to the thread axis.
The Junker diagram shows Nord-Lock®'s unique locking effect. Only minor pre-tensioning force losses occur due to normal settlement processes between the parting lines and the thread. The wedge-locking action is confirmed by the significant increase in clamping force during the loosening process. Conventional locking elements do not display locking action when subjected to vibration.