What are the common methods for preventing loose nuts?


Anti-loosening of friction, this method generates a pos […]

Anti-loosening of friction, this method generates a positive pressure between the thread pair that does not change with external force, so as to produce a friction force that can prevent the relative rotation of the thread pair. This positive pressure can be achieved by pressing the thread pair axially or simultaneously in two directions. Common friction and anti-loosening are: the use of gaskets, self-locking nuts and double nuts.
The material of the spring washer is spring steel. After assembly, the washer is flattened, and its rebound force can maintain the pressing force and friction force between the threads, thereby achieving anti-loosening. The anti-loosening of the top nut is to use the action of the nut against the top to subject the bolt type to additional tension and additional friction. Because one more nut is used, and the work is not very reliable, it has been used less and less. Self-locking nut anti-loosening is that one end of the nut is made into a non-circular closing or radial closing after slitting. When the nut is tightened, the closing part expands, and the elasticity of the closing part is used to make the screw threads tight. The anti-loosening structure is simple and reliable, and can be disassembled and assembled many times without reducing the anti-loosening performance.
The elastic ring nut anti-loosening is to embed fiber or nylon into the thread to increase the friction. The elastic ring also serves to prevent liquid leakage. This anti-loosening method is more convenient for the disassembly of the nut, but in the case of impact, vibration and variable load, the preload force will be reduced due to slack at the beginning. As the number of vibrations increases, the loss of preload force increases slowly Will eventually lead to loosening of the nut and failure of the threaded connection.
Mechanical anti-loosening, this way is to use the stopper to directly limit the relative rotation of the screw pair. Common mechanical anti-loosening methods: use cotter pins, stop washers and stringed steel ropes.
The slotted nut and cotter pin are anti-loosening. After the slotted nut is tightened, use the cotter pin to pass through the small hole at the tail of the bolt and the slot of the nut. Or you can use a common nut to tighten and drill the pin hole.
Round nut and stop washer so that the inner tongue of the washer fits into the groove of the bolt (shaft). After tightening the nut, fold one of the outer tongue of the washer into a groove of the nut.
After the locking washer and the nut are tightened, bend the single-ear or double-ear stop washer to the side of the nut and the connected piece respectively to achieve tightness. If the two bolts need to be double-locked, double-lock stoppers can be used.
The steel wire in series is loose, and the low carbon steel wire is inserted into the hole of the head of each screw, and the screws are connected in series to make each other brake. This structure needs to pay attention to the direction in which the steel wire penetrates, which makes disassembly inconvenient.
Riveting, punching and anti-loosening is to use punching point, welding, bonding and other methods after tightening, so that the thread pair loses the characteristics of the motion pair and the connection becomes a non-detachable connection.
Punching method to prevent loosening is to break the thread at the end of the thread after the nut is tightened; the adhesive is usually applied to the threaded surface of the thread with anaerobic adhesive. After tightening the nut, the adhesive can be cured by itself, and the anti-loosening effect is good. . The disadvantage of this method is that the bolt can only be used once, and it is very difficult to disassemble, and the bolt pair must be destroyed before it can be disassembled.
The structure is anti-loosening, using the thread pair's own structure to solve the treatment of thread teeth. Namely, Tang's thread anti-loosening method, and Shi Bilao anti-loosening method. This method can be disassembled repeatedly, and the anti-loosening performance is the best.