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Types and applications of threaded fasteners

The role of aviation fasteners: the tens of thousands of functions of the aircraft: the tens of thousands of parts of the aircraft are connected to form a whole; when carrying, the load is transmitted and the deformation is coordinated.

Threaded fastener

Threaded fasteners: bolts, screws, washers and nuts - multiple disassembly and assembly

The spiral ------ the moving point is on the surface of a cylinder, and rotates at a constant speed around the axis while moving in the axial direction at a constant speed.

Thread ------The plane pattern moves along the helix, and when the motion is maintained, the pattern passes through the axis of the cylinder, and the thread is obtained.

The difference is as follows: 1. The coarse thread series of the same size number has the same thread nominal diameter as the thread of the fine thread series, but the number of teeth per inch length is different.

2. The tolerances are different; there are also different thread sizes for 1 inch diameter:

NF regulations - 14 teeth per inch, expressed as 1 - 14 NF

UNF regulations - 12 teeth per inch, expressed in 1 - l2UNF

Matching level

• The thread is also graded. The grade of the thread indicates the degree of tightness of the thread pair. It has five levels:

• Level 1 - loose fit (just turn the nut easily with your fingers)

• Level 2 - Free fit (used by aviation screws)

• Level 3 - Moderate fit (used by most aviation bolts)

• 4, 5 - tight fit (requires a wrench to screw the nut)

The greater the number of grades, the tighter the tightening of the thread pair.

Types and applications of threaded fasteners

Bolt-transfer shear and tensile loads

Application: Large concentrated load or parts that need to be disassembled

Category: Pulled mainly

Subjected to shear