Over long-term use, nuts often loosen due to factors such as vibration and impact, affecting the normal operation of equipment. To ensure effective nut tightening, three common methods for preventing loosening have been developed. We will now introduce these methods one by one.
▲ 1. Nut Preventing Loosening
The three common methods for preventing nut loosening include friction, mechanical, and permanent locking.
1.1 ▲ Friction Preventing Loosening
Friction preventing loosening primarily relies on components such as counter-nuts, spring washers, and self-locking nuts to prevent nut loosening by increasing friction.
1.1.1 ▲ Spring Washer Preventing Loosening
Spring washers, made of spring steel, are flattened during assembly. Their rebound force maintains constant compression and friction between the threads, thereby preventing loosening.
1.1.2 ▲ Counter-nut Preventing Loosening
The counter-nut action of the nut applies additional tension and friction to the bolt. However, because it requires an additional nut and its effectiveness isn't completely reliable, this method is now less commonly used.
1.1.3 ▲ Self-Locking Nuts
The design of self-locking nuts features a carefully crafted, non-circular cuff or slot on one end. This allows the cuff to expand during tightening. Once the nut is tightened, the elastic force of the cuff acts to tightly compress the threads. This anti-loosening method is not only simple and easy to understand, but also highly reliable, maintaining its effectiveness even after repeated disassembly and assembly.
1.1.4 ▲ Elastic Ring Nuts
Elastic ring nuts feature a fiber or nylon material strategically embedded in the threaded entry area. This design not only increases friction but also effectively prevents fluid leakage.
1.2 ▲ Mechanical Anti-Locking
Mechanical anti-loosening methods are commonly used, including the use of cotter pins and hexagonal slotted nuts, lock washers, and tandem wires. These methods effectively ensure the tightness of critical connections.
1.2.1 ▲ Anti-loosening Applications of Castle Nuts and Cotter Pins
After tightening a castle nut, a cotter pin can be used to prevent loosening by inserting it through a small hole at the end of the bolt and the slot in the nut. Alternatively, after tightening a regular nut, a cotter pin hole can be drilled to prevent loosening. This method uses the castle nut and cotter pin to secure the bolt and nut, preventing loosening.
1.2.2 ▲ Anti-loosening Methods of Round Nuts and Lock Washers
The inner tongue of the washer fits into the slot of the bolt or shaft. The nut is then tightened, and one of the folds of the outer tongue of the washer fits into one of the slots in the nut, achieving an anti-loosening effect. This anti-loosening method uses the inner tongue of the washer to fit into the bolt, and the outer tongue to fit into the slot in the nut.
1.2.3 ▲ Anti-loosening Methods of Lock Washers
After tightening the nut, bend a single-ear or double-ear lock washer so that it rests against the sides of the nut and the connected component, thereby preventing loosening. When double locking of two bolts is required, double locking washers can be used.
1.2.4 ▲ Series Wire Locking
By inserting mild steel wire into the holes in each screw head, the two screws are connected in series, creating a mutual lock. When implementing this locking method, pay special attention to the direction of the wire insertion. This method inserts the mild steel wire into the screw hole to create a series lock.
1.2.5 ▲ Permanent Locking
Threaded fasteners are secured against loosening using methods such as spot welding, riveting, or gluing. However, these methods often damage the threaded fasteners during disassembly and are therefore not reusable. Permanent locking is achieved through welding, riveting, and other methods.
In addition, there are various other locking methods, such as applying liquid adhesive between the threads, inserting nylon rings into the ends of nuts, and using mechanical and frictional locking methods such as rivets. These methods are often referred to as removable locking, as opposed to permanent locking.