Flat Head Allen Socket Sleeve Collared Hex Nut

According to the performance characteristics and functions of the used fasteners, the fasteners used in many fields will use stainless steel, and the most common disadvantage of stainless steel fasteners is the problem that the bolts and nuts can not be loosened after matching in the process of use. This phenomenon is "bite". Usually, we can also call it "lock".

Why do Stainless Steel Holding Down Bolts and nuts have this problem? How can we prevent the stainless steel fasteners from biting?

Once the bolt and nut are locked in use, the two fasteners will be difficult to separate. [Flat Head Allen Socket Sleeve Nut]Usually, we will cut off the bolts or break the nuts to realize the disassembly of accessories, which will directly affect the disassembly rate of accessories and the reusability of fasteners. Therefore, we need to analyze the principle and causes of the seizure of Stainless Steel Holding Down Bolts, and then find out the most reasonable preventive measures to prevent the seizure of fasteners, bolts, and nuts.

Principle of seizing between stainless steel bolt and nut

Stainless steel fasteners have rust resistance, which will produce a thin oxide layer on the metal surface when the surface is damaged to prevent further corrosion. [Allen Socket Sleeve Nut]When the stainless steel fastener is locked, the pressure and heat generated between the teeth will destroy and erase the chromium oxide layer between them, so that the metal teeth will directly block / shear, and then adhere. When the adhesion phenomenon continues to occur, the stainless steel fasteners will be completely locked and can no longer be removed or locked. Usually, this series of blocking → cutting → sticking - → locking takes place in just a few seconds.

Causes of seizure of Stainless Steel Holding Down Bolts and nuts

By analyzing the principle of the biting phenomenon of stainless steel fasteners, it can be seen that the biting of Stainless Steel Holding Down Bolts is caused by the direct contact and further development of metal materials due to the destruction of the oxide layer by the pressure or heat between the teeth. [Collared Hex Nuts]Therefore, the excessive pressure or heat between the teeth often causes the biting phenomenon of Stainless Steel Holding Down Bolts. For the following reasons, excessive pressure or heat is often generated between the teeth, and then the stainless steel fasteners bite.

• The tooth lines are rough or foreign matters stick. If there are solder joints and other metal chips sandwiched between the teeth, it will often lead to biting death.

• The tightening force is too large or the tightening speed is too fast. Excessive tightening force is easy to cause greater pressure between teeth lines and leads to biting; If the tightening speed is too fast, the temperature between teeth will rise rapidly and bite.

• The angle of force application direction is wrong. When tightening, the tightening direction is not perpendicular to the axial direction of the bolt, which is easy to cause a seizure.

Preventive measures for seizing Stainless Steel Holding Down Bolts and nuts

Through the previous analysis, it can be seen that the disassembly of Stainless Steel Holding Down Bolts after being bitten is extremely inconvenient, and even some methods or special tools are time-consuming and laborious. Therefore, it is particularly important to prevent stainless steel fasteners from being bitten. The following introduces several methods to prevent the bite of Stainless Steel Holding Down Bolts.

• Bolts and nuts of different materials shall be selected for matching.

• Improve the performance of fasteners, such as adding film on the threads of fasteners to prevent seizure, but this method has a high cost and is rarely used at present.

• Clean the thread, check that the tooth lines are complete and continuous and that there are no impurities between the tooth lines.

• The thread shall be applied with lubricant, such as molybdenum disulfide, grease, etc., which shall be evenly applied and filled with the threaded bottom, covering the bolt head with a length of about (10 -15) mm.

• When tightening, first screw the nut or bolt into (2-3) thread by hand, and then tighten it with a torque wrench or simple wrench. The tightening force shall be uniform, and the tightening direction shall be perpendicular to the axial direction of the bolt. Movable wrench or electric and pneumatic wrench shall not be used as far as possible.

• When pre-tightening with an electric or pneumatic wrench, avoid excessive torque or speed. Ensure that the nut stops using when it contacts the cushion, and then tightens with a torque wrench. The tightening torque shall not exceed the specified torque value.

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