There is a wide variety of industrial fasteners for example nuts, bolts, screws, washers, studs and many others. Nuts and bolts are a significant family of fasteners called threaded connections. Threaded connections are used widely in many manufacturing applications. The main advantage of threaded connections is, they stay together when we want them to and come apart if a need to have them disconnect arises. Vehicle engines, for instance, should stay together while driving no matter the vibrations and also easily be dismantled during servicing. There is, therefore, need for a reliable way to lock the connection together to ensure the lock does not loosen in during operation.
Lock washers compressed from preload.
Components are threaded together to create what is known as an axial preload. The tensile force subjected to a bolt during tightening is known as preload. This force behaves such that it produces a sort of clamping force between the nut and the bolt. The helix angle of the bolt should, however, be such that it creates a joint that is self-locking. Sustaining a correct preload that is 50% to 90% of the bolts yield strength will ensure this self-locking (Bickford " Nassar, 1998).
Nord-lock washers
Unlike lock washers, Nord-lock washers secure joints with tension rather than friction. It is made up of two washers with a series of serrations on the outside and a series of cams on the inside. These serrations ensure that the only rotation that is possible is a rotation between the cams. It designed such that the cam angle is always greater than the thread pits, therefore, creating a wedge effect. This prevents unintentional rotation of the bolt while at the same time locking the mechanism; the tension created makes the bolt/nut self-locking (Vangelder, 2018).
Adhesives
Thread-locking adhesives prevent bolts and nuts from loosening by filling the tiny spaces between interlocking threads. These liquids turn into tough solids immediately they touch metal (Silva, Pirondi, " Öchsner, 2011).
Types of coatings to weatherproof fasteners
Clear zinc
Clear zinc is the most widely used fastener coating in the world because it is both effective in protecting fasteners and cheap. It is mainly designed to protect fasteners from oxidative failure. Clear zinc is used primarily to preserve fasteners from rust. It is most suitable for use under humid conditions (Paul, 1942).
Gray phosphate
It is also designed to protect fasteners against corrosion. It, however, provides a low-level protection it is therefore not suitable for applications where the risk of erosion is high. This type of coating is entirely unsuited for marine applications. This coating is suitable only for relatively dry applications and even such conditions it should be applied properly (Paul, 1942).
Yellow zinc
Unlike the previous two, this is applied electrically by a process called electrodeposition. It is also suitable for applications that happen under humid conditions. It protects fasteners that will likely come into contact with water. Like gray phosphate, it has to be appropriately applied to work effectively. Zinc protects through a process called galvanic erosion (Paul, 1942).
Alternative assembly and finishing methods
Rivets are a better alternative for fastening. Rivets do not loosen if subjected to vibration loading. They can also secure a joint with a relatively short clamp length. Welding too has advantages over bolts in that it offers low stresses compared to bolts. Bolts concentrate stress on each bolt while welds spread it across the weld. Cadmium plating is a better alternative to zinc plating because it offers better lubricity (Geary " Miller, 2011).
Bibliography
Bickford, J " Nassar, S., 1998. Handbook of bolts and bolted joints, New York: Marcel Dekker Inc.
Geary, D., " Miller, R. 2011. Welding. New York, McGraw-Hill.
Paul, T., 1942. Zinc yellow in the inhibition of corrosion-fatigue of steel in sodium chloride solution.
Silva, M., Pirondi, A., " Öchsner, A., 2011) Hybrid Adhesive Joints.
Vangelder, T., 2018. Fundamentals of automotive technology: principles and practice
