Hexagon nut and bolt, screw with the use of connection fastening parts. The I type hex nut is widely used, and the C grade nut is used for the machine, equipment or structure with rough surface and low accuracy requirements. Class A and CLASS B nuts are used on machines, equipment or structures with relatively smooth surfaces and high precision requirements. II hexagon nut thickness m thicker, often used for often need to assemble and disassemble occasions. The thickness of the hexagonal thin nut m is thinner, and it is used for the occasions where the surface space of the connected parts is limited.
Hexagon nut according to the nominal thickness is divided into type I, TYPE II and thin type three. Nuts above grade 8 are divided into two types: Type I and type II.
Type I hexagonal nut is widely used, type 1 nut is divided into A, B, C level 3, which A and B nut is suitable for the surface roughness is smaller, the precision of the machine, equipment and structure, and the C nut is used for the surface roughness, the precision of the machine, equipment or structure is not high;
The thickness of type II hexagon nut is relatively thick, and it is often used in the occasion of assembly and disassembly.
Type I nut refers to ordinary hexagonal nut with nominal height m≥0.8D, and its type size should conform to the provisions of GB/T6170;
The height of type II nut is higher than that of type 1 nut, and its type size should conform to GB/T6175. The purpose of increasing type II nuts has two: one is to increase the height of the nut to get a kind of heat treatment, relatively cheap nut.
Because D≤M16 class 8 type I nuts do not need heat treatment, so in class 8 nuts, only the specifications of D>M16~39 type 2 nuts are used.
Obviously, type I nuts without heat treatment cannot meet the mechanical properties requirements of class 9 nuts. Another purpose of specifying type II nuts is to obtain grade 12 nuts with better toughness. As the height of the nut increases, the guaranteed stress index can be achieved at a lower quenching and tempering hardness, so the toughness of the nut is increased.
Classification by pitch: standard teeth, normal teeth, fine teeth, very fine teeth and counter teeth.
According to the material classification: stainless steel hexagon nuts and carbon steel hexagon nuts, copper hexagon nuts, iron hexagon nuts.
Classification by thickness: hexagonal thick nuts and hexagonal thin nuts.
Classification by using method: hot melt copper nuts, hot pressed copper nuts, embedded copper nuts and ultrasonic copper nuts.