There are three common methods to prevent hexagonal nuts from loosening: friction, mechanical and permanent.\
1. Friction, used for hexagonal nuts, spring washers, self-locking hexagonal nuts, etc.
(1) Spring washer to prevent loosening
The material of the spring washer is spring steel. After the washer is assembled, it is flattened. Its rebound force can maintain the compression and friction between the threads, thereby preventing loosening
(2) Hexagonal nut to prevent loosening
Hexagonal nuts are used for lifting actions, so that the bolt type bears additional tension and additional friction. Since an extra hexagonal nut is used and the work is not very reliable, it is used less and less at present.
Hexagonal locking nut
(3) Self-locking hexagonal nut to prevent loosening
One end of the hexagonal nut is made into a non-circular closure or radial closure after the slit. When the hexagonal nut is tightened, the closure expands and the elastic force of the closure is used to tighten the thread. The anti-loosening structure is simple and reliable. It can be disassembled and assembled many times without reducing the anti-loosening performance.
(4) Elastic ring hexagonal nut anti-loosening
Fiber or nylon is embedded in the threaded entrance to increase friction. The elastic ring can also prevent liquid leakage.
2. Mechanical anti-loosening, use: cotter pins and hexagonal slotted hexagonal nuts, stop washers, series steel wires, etc.
Mechanical anti-loosening methods are more reliable, and important connections should use mechanical anti-loosening methods.
(1) Slotted hexagonal nuts and cotter pins to prevent loosening
After the slotted hexagonal nut is tightened, use the cotter pin to pass through the small hole at the end of the bolt and the slot of the hexagonal nut, or tighten it with an ordinary hexagonal nut and drill the pin hole.
(2) Round hexagonal nut and stop washer
Insert the inner tongue of the washer into the groove of the bolt (shaft), and after tightening the hexagonal nut, fold one of the outer tongues of the washer into the groove of the hexagonal nut.
(3) Stop washers
After tightening the hexagonal nut, bend and connect the single-ear or double-ear stop washers to the side and connection part of the hexagonal nut respectively to prevent loosening. If you need to double-lock two bolts, you can use a double-joint stop washer.
(4) Series wire anti-loosening
Use low-carbon steel wire to pierce the holes on each screw head and connect the screws in series so that they brake each other. This structure requires attention to the direction of wire penetration.
3. Permanent anti-loosening, use: spot welding, riveting, bonding, etc.
This method will mostly damage the threaded fasteners during disassembly and cannot be reused.
In addition, there are other anti-loosening methods, such as: applying liquid adhesive between the threads, inlaying nylon rings at the end of the hexagonal nut, riveting punching anti-loosening, mechanical anti-loosening and friction anti-loosening are called removable anti-loosening, while permanent anti-loosening is called non-removable anti-loosening.
(1) Punching method to prevent loosening
After tightening the hexagonal nut, the punch at the end of the thread will damage the thread
(2) Bonding and anti-loosening
Anaerobic adhesive is usually applied to the thread surface. After tightening the hexagonal nut, the adhesive can cure by itself, and the anti-loosening effect is good.