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Why are bolts and nuts loose?

Nov 17,2022

The China Hex Bolts Suppliers and nut are combined as a set of fasteners to keep butt joint. The internal (internal) thread on the nut shall correspond to the external (external) thread of the bolt. In some cases, gaskets are added in combination with these two components to help distribute the received loads and forces around. The process can resist the cracking and fracture of fasteners.
Bolts and nuts have self loosening and pre tightening force loss. When this happens during assembly, it may change the function of the bolt, resulting in adverse consequences. The reason for selecting bolts is that their quality can provide strength and durability. The loose bolt will destroy their purpose, which is why it is important to prevent them from happening.
Spontaneous loosening of bolts (due to impact, vibration and dynamic load)
Spontaneous loosening, also known as rotational self loosening, is the most common cause of bolt failure. This occurs when the bolt rotates due to vibration or dynamic load and impact. Eliminating slip between joints or at least lowering them below the critical level is one of the best options to prevent loosening of bolts. Another method is to use fastener lubricant or adhesive to increase the friction between bolt and China Wood Screws Suppliers threads. For safer assembly, the aviation industry also uses locking wires.
Relaxation (result of settlement, creep and relaxation)
Settlement is considered critical because it occurs as a result of dynamic loading. Permanent deformation or fatigue of clamping materials and joints will increase the stress of dynamic working load. Creep occurs when fasteners are exposed to high levels of stress that exceed the yield strength of the material for a long time. It is very serious under high temperature. When the existing elastic properties are transformed into plastic deformation over time, relaxation is the reorganization of the microstructure in the material.
The key to avoiding bolt relaxation type is good design and high pre tightening force of bolts.
Insufficient tightening
By definition, they are loose applications of bolts that make the clamping force insufficient to hold the various parts of the joint together. Inadequate tightening will lead to sliding between parts and produce unnecessary shear stress, which will eventually lead to bolt fracture.
2. Vibration and shock
Vibration is a lateral motion that causes two parts of a joint to move parallel to each other. Nuts and bolts can only bear the maximum friction force from repeated movement before loosening from the mating thread and losing the clamping force.
Impact is a dynamic or alternating load, such as a sudden force applied to a joint. Only the vibration in this repeated sequence will eventually cause the bolt to loosen.
3. Embedding
When the bolt is poorly designed and not tensioned, the embedded joint will result in a loss of clamping force. The micro insertion of bolts and nuts is a process that allows them to reach a specific tension.
Gasket creep
In the usual assembly of bolted joints, a flexible washer is inserted between the head and the surface to completely seal the joint to prevent gas or liquid leakage. The washer also acts as a spring to push the pressure on the bolt and joint face. Over time, due to the destructive factors of high temperature and corrosive chemicals, gaskets may creep (lose elasticity) and lead to the loss of clamping force.

Finish:Black, Black Oxide, Blue Anodized, BLUE DYED, Cadmium Plated, Chrome Plated, Plain, Silver Plated, ZINC, ZINC PLATED, Zinc-aluminum Coated, Zinc-Flake Coated
Material:Stainless Steel, Steel
Measurement system:INCH, Metric
Head Style:Cheese, Flat, HEX, Oval, Pan, Round, Truss
Place of Origin:China
finish:plain,HDG,zinc plated
materal:steel,stainless steel,carbon steel
type:metal roofing screws for wood
customed:as the drawing
thread:wood screw
Certificate:ISO9001: 2015

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