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Method For Preventing Loosening Of Bolts

Nov. 30, 2019 | 10:50:53
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Loose bolts are common, but if you don't pay attention, it will often cause equipment vibration, component damage, and even casualties. How to tighten a small nut has always been a long-lasting topic in mechanical design. Today, we will talk to you about the most basic method of fixing nuts at work by Expansion Bolt Supplier.


There are three commonly used methods of nut loosening prevention: frictional loosening, mechanical loosening, and permanent loosening.


First, friction prevention

Double nut anti-loosening, spring washer, self-locking nut, etc.

1, leveling washer

A washer refers to a part cushioned between a connected member and a nut, generally a flat metal ring, which is used to protect the surface of the connected member from being scratched by the nut and disperse the pressure of the nut on the connected member.

2. Flat washer and spring washer

Spring washers are widely used in the bearing and non-bearing structures of general mechanical products. They are characterized by low cost, convenient installation, and suitable for frequent assembly and disassembly, but the spring washers have a low ability to prevent loosening!

3.Self-locking nut

The ordinary nut will loose itself due to other reasons such as vibration during use. In order to prevent this phenomenon, a self-locking nut was invented. The function of self-locking nut is mainly to prevent loosening and anti-vibration, which is used for special occasions. Its working principle is generally self-locking by friction. Types of self-locking nuts classified by function include embedded nylon rings, necked necks, and metal anti-loosening devices. They are all effective torque-type anti-loosening nuts. Due to its nature, self-locking nuts are difficult to screw.

4.Double nut anti-loosening

Double nut anti-loosening is that after tightening two nuts with the same rotation direction, twist the two nuts in the direction of the arrow to make a pairing force between the two nuts, so that the bottom nut can cause friction with the washer. , And friction with the second nut, double friction to achieve the effect of pre-tightening.

5. Anti-loosening of elastic ring nut

Fiber or nylon is embedded in the threaded entry to increase friction. The elastic ring also functions to prevent liquid leakage.


Expansion Bolt


Expansion Bolt 


Second, mechanical anti-loosening

Split pin with Hexagonal Nut, stop washer, tandem wire, etc.

Mechanical anti-loosening methods are more reliable. For important connections, mechanical anti-loosening methods should be used.

1. Screw and nut drilling and pin fixing

In machinery, pins are mainly used for assembly positioning, and can also be used as overload, shear-break connections in connection, anti-loose safety devices. The types of pins are: cylindrical pin, conical pin, perforated pin, split pin and safety pin.

2.Round nut and stop washer

The inner tongue of the washer is inserted into the groove of the bolt (shaft), and after tightening the nut, one of the outer tongue of the washer is folded into a groove of the nut.

3.Stop washer

After the nut is tightened, the one- or two-ear stop washers are respectively bent and fastened to the side of the nut and the coupled part to prevent loosening. If two bolts are required to be double-locked, double-locking washers can be used.

4.Tandem steel wire for loosening prevention

Use a low-carbon steel wire to penetrate the hole in the head of each screw, and connect the screws in series to brake each other. This structure requires attention to the direction in which the wire penetrates.


Third, permanent anti-loosening

Spot welding, riveting, bonding, etc.

This method often destroys the threaded fasteners during disassembly and cannot be reused.


Fourth, there are other ways to prevent loosening, such as: coating liquid adhesive between the screw threads, inlaying nylon rings at the end of the nut, riveting and punching to prevent loosening. Mechanical and frictional locks are called removable locks, and permanent locks are called non-removable locks.

1. Punching method to prevent loosening

After the nut is tightened, a punch at the end of the thread destroys the thread.

2. Bonding anti-loosening-nut anti-loosening fluid

Apply the nut anti-loosening solution to the tightening position of the bolt, and then screw on the nut. After curing by itself, the anti-loose effect is good.


The above is the bolt loosening prevention method shared by Fastener Bolt Supplier. Have you learned it?