Hexagon nut (Hexagon nut) is used in conjunction with bolts and screws to connect and tighten the parts. 
Among them, type I hexagonal nuts are more widely used, class C nuts are used in machines, equipment or structures with rough surfaces and low requirements for precision, and class An and B nuts are used in machines, equipment or structures with relatively smooth surfaces and high precision requirements. 
The thickness m of type II hexagonal nut is relatively thick, so it is often used in occasions where assembly and disassembly are often needed. 
The thickness m of the hexagonal thin nut is thin, so it is mostly used in the situation where the surface space of the connected parts is limited. 
A nut is a fastener with an internal thread used with a bolt, a mechanical part with an internal thread and used with a screw to transfer motion or power. 
A nut is a nut, a part screwed with a bolt or screw to tighten, an original that all manufacturing machinery must use. 
There are many kinds of nuts. We have national standard, British standard, American standard and Japanese standard nuts. 
According to the different materials, nuts are divided into carbon steel, high strength, stainless steel, plastic steel and other types. 
According to the product attributes corresponding to different national standard numbers are divided into ordinary, non-standard, (old) national standard, new national standard, American system, English system, German standard. 
Different sizes, different threads are divided into different specifications. 
General national standards and German standards are represented by M (for example, M8, M16), while American and English standards use fractions or # to indicate specifications (such as nuts, 1mm, 1x4, 3pl8) fasteners. Nuts are parts that closely connect mechanical equipment. Nuts and screws of the same size can only be connected together through the inner thread. For example, nuts of M4-0.7 can only be matched with nuts of M4-0.7 (in nuts). 
The inner diameter of M4 finger nut is about 4mm. (the distance between two threaded teeth is 0.7mm). 
The same is true of American products, for example, the nut of 1 hand 4-20 can only be matched with the screw of 1 hand 4-20 (the inner diameter of 1 hand 4-finger nut is about 0.25 inch, 20 fingers have 20 teeth per inch).