We have all experienced loose screws or nuts. Whether it’s a loose fastener on a piece of machinery or on our glasses, it happens. But it doesn’t have to; what causes the loosening of fasteners and how can you prevent it?
How to Prevent Fasteners Loosening
To understand what causes fasteners to loosen, it is important to understand the self-locking principles of a joint. When tightening a fastener, friction is introduced in the thread and bearing areas. Maintaining this friction is the key to preventing fasteners from coming loose. External, dynamic forces, such as vibration can result in loss of friction, causing the fasteners to rotate loose if the forces are high enough. One way to prevent this is to ensure proper clamp load into the joint and use longer bolts with clamping range of at least 5x’s the diameter. This causes the bolt to act like a spring, and not lose friction when external forces act upon it.
Using Nord-Lock Washers
Often times joints cannot be designed with longer bolts, or proper clamp load cannot be guaranteed. For these joints, a Nord-Lock washer should be considered. This special serrated locking washer always comes as a pair of two washers to deliver the locking effect. The outer surfaces are ribbed and will bite into even the hardest materials, while the inner surfaces have precision ground ramps with an angle slightly greater than the pitch angle of the threads. After the joint is tightened, if the screw tries to rotate loose, the upper washer will rotate and separate slightly from the lower one. The rotational loosening of the screw is stopped as the clamp load increases slightly during the rotation.
Nord –Lock washers are a practical option to stop loosening fasteners since they may be re-used many times and only require slightly higher torque to achieve your required clamp load.
Have you used Nord-Lock washers? Tell us about your experience below!
Learn more about Nord-Lock washers by contacting us at ProvenProductivity@bossard.com.
Use Nord-Lock to Stop Fasteners from Loosening by Bossard