7 ways to firmly fix bolts in 2026

Do you think that once the bolt is tightened, it won’t loosen? However, in the face of high-frequency vibration mechanical equipment, ordinary fastening methods are often ineffective. Take high-strength bolts on train chassis for example, they can still loosen under continuous impact and bumps. Some people say that I can tighten them very tightly with all my strength. This will only backfire. Once the force exceeds the expected tightening limit, the bolt will directly break physically. It cannot be tightened beyond the limit, but it needs to be ensured to loosen. What should we do? Today, we will dismantle seven types of bolt anti loosening structures.

The first type of spring washer
Intuitively speaking, as long as it is tightened and flattened, it can continuously provide axial rebound force to prevent the nut from loosening. However, in the Junker vibration test, engineers found that once the equipment experiences severe lateral sliding, the tension of the spring washer will instantly return to zero, and the anti loosening effect will completely fail.

So, for this reason, engineers made some improvements on the basis of the spring washer and designed a double piece wedge-shaped washer. Its outer side is hardened serrations, and the inner side is a sloping surface with a slope. When installing, the two sloping surfaces are attached to each other. After tightening, the outer serrations are directly stuck into the metal surface, forcibly locking the upper and lower ends. Because the outer side has been completely stuck by the contact surface, once the vibration causes retraction sliding, it can only occur between the two sloping surfaces in the middle of the washer. This is the core mechanism of anti loosening. The slope angle inside the washer is greater than the upward angle of the thread. As long as the nut retracts and rotates, it will inevitably climb up along the internal slope and forcefully push the bolt upwards. The machine vibrates more violently. The greater the force on the top of the slope, the tighter the bolt is pulled, Both of the previous solutions rely on external gaskets. If you don’t have a special gasket in hand, how can you prevent loosening with only the most basic standard parts.

Let’s take a look at the third type of double nut tightening
Just need two nuts, one thin and one thick, on the bolt. The core of anti loosening lies in the final locking action.

Two wrenches operate simultaneously, with the thick nut pressing downwards and the thin nut retracting upwards. This opposing force will completely squeeze the thread gap and lock the metal tooth surface in place.
If you find this type of double nut cumbersome, engineers have a more extreme solution, which is to work inside a single nut. This is the fourth type of self-locking nut, which is divided into two categories. The first type is nylon self-locking nut, with a non threaded nylon ring at the top. When the bolt is screwed into this area, the thread will be forcibly squeezed out on the nylon ring, using the high elasticity and high damping characteristics of nylon to produce a strong mirror tightening force on the bolt.

The second type is the all metal flattened nut, whose top has been mechanically stamped into a small oval shape at the factory
When a perfectly circular bolt is screwed in, the elliptical port must be forcefully flattened, relying solely on the elastic rebound of the metal. The flattened metal port will contract inward, completely clamping the bolt around and achieving pure physical locking.

In addition to modifying the mechanical structure, there is another method to solve the problem through chemical means, which is the fifth method. Directly apply anaerobic adhesive to the threads. As long as this liquid is applied to the threads, tightened and isolated from air, it will quickly solidify in the metal gaps, like ordinary physical locking, leaving small gaps between the threads. The essence of anaerobic adhesive is to turn into hard plastic, completely fill and block these gaps, and integrate the entire threaded joint.

If you don’t use glue and want to completely lock it with a pure physical structure, let’s look at the sixth type, which is a groove nut with an opening cut. However, this structure needs to be customized. The top of the nut is cut with a uniform groove, and the end of the bolt is reserved with a horizontal through hole. When installing, tighten the nut first, adjust the angle slightly to align the groove and the hole into a straight line, and then take a metal opening cut directly across it. Finally, cut the end of the opening in half and forcefully bend and stick it to both sides. As long as the metal is not cut hard, the nut will be firmly clamped.

The previous solutions are all aimed at a single fastener. For aircraft engines with zero fault tolerance, let’s take a look at the ultimate solution. The seventh method is aviation grade series steel wire, which is specifically designed to deal with key bolts in groups. Each bolt has a small hole reserved at the hexagonal head, and then a high-strength stainless steel wire is used to pass through the holes of the entire bolt group in sequence. Then, a special tool is used to tighten it into a spiral shape. Once a bolt is shaken and rotates, the wire will be immediately tightened, forcing adjacent bolts to bear the tension in the tightening direction. Through this wire, a perfect rigid protection is formed between the bolt group

The above are seven common bolt anti loosening structures, which can be locked according to the type of vibration, and can only be truly foolproof by taking targeted measures.