Common national standards for nuts

GB41 Type I Hex Nut - Class C
GB6170 Type I hex nut - Class A, Class B
GB6171 Type I hex nut - fine teeth - Class A, Class B
GB6172 Hexagon Thin Nut - Class A, Class B - Chamfer
GB6173 Hexagonal Thin Nut - Fine Teeth - Class A, Class B
GB6174 Hexagonal Thin Nut - Class B - No Chamfering
GB6175 Type II Hex Nut - Class A, Class B
GB6176 Type II Hex Nuts - Fine Teeth - Class A, Class B
GB6177 Hex Flange Face Nut - Class A
GB56 hexagonal thick nut
GB1229 large hex nut (high strength for steel structure)
Bolt coarse and fine tooth usage;
(1) Fine thread thread is good for anti-vibration, easy to adjust the gap, but the lock mother force is worse than coarse teeth. Suitable for places where the gap or torque should be adjusted.
(2) The self-locking ability of coarse thread is worse than that of fine tooth, but the locking force is larger than that of fine teeth. Generally, there is no special requirement for coarse thread.
Coarse thread: directly follow the thread diameter after M, without marking the pitch,
Labeling and not marking the pitch is the difference between ordinary fine thread and ordinary coarse thread.
The grades of metric bolts are: 4.6; 4.8; 5.8; 6.8; 8.8; 9.8; 10.9; 12.9.
The grades of the metric nuts are: 4; 5; 6; 8; 10; 12 where 4; 5 is the strength grade of the thin nut.
You said that the nut A; B; C level is equivalent to the US G2; G5; G8 performance level, J995 stipulates that the performance level between the two is basically the same!
Type 1 nut thread size is M1.6~M64 Performance class is 6; 8; 10; A2-50; A2-70; A4-50; A4-70; CU2; CU3 and AL4, product grades A and B , Class A is used for specifications less than or equal to M16; Class B is used for specifications larger than M16! (A here; B refers to the accuracy level)
Type 2 nut thread size is M5~M36, performance grade is 9 and 12 grades, product grade is A and B grade, grade A is used for specifications less than or equal to M16; grade B is used for specifications larger than M16! (A here; B refers to the accuracy level)
Due to the high performance requirements of Type 2, the thickness of the nut is thicker.
Bolt performance grades are divided into more than 10 grades of 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, the bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel and heat treated (quenched, back) Fire), commonly known as high-strength bolts, the rest are commonly referred to as ordinary bolts.

The bolt performance grade label is composed of two parts, which represent the nominal tensile strength value and the yield ratio of the bolt material. For example, a bolt with a performance class of 4.6 means:
Performance class 4.6 bolts, meaning
1. The nominal tensile strength of bolt material is up to 400MPa;
2, the bolt material has a yield ratio of 0.6;
3, the nominal yield strength of the bolt material is 400 × 0.6 = 240MPa

Performance class 10.9 high-strength bolts, the material can be reached after heat treatment
1. The nominal tensile strength of bolt material is up to 1000MPa;
2, the bolt material has a yield ratio of 0.9;
3, the nominal yield strength of the bolt material is 1000 × 0.9=900MPa
The meaning of the bolt performance grade is the international standard. The bolts of the same performance grade have the same performance regardless of the difference between the material and the place of origin. Only the performance grade can be selected in the design.

Chamfering