Standards and grades of external hexagon bolts

Standard for external hexagon bolts:

The standard for external hex bolts stipulates that the thread specification is M3-M64. Among the external hex bolts A and B, grade A is used for D <= 24 and L <= 10D, or L <= 150mm bolts, and grade B is used for D> 24, or L> 10D, or L> 150 bolts. The specification of the external hexagon bolt is D = M12, the nominal length is L = 80mm, and the performance grade of the external hexagon bolt is 8.8. Hexagon bolts are the most frequently used among all types of bolts in daily life. The main function of external threads possessed by external hexagon bolts is to cooperate with nuts. The use of this thread connection method can make two Parts fit.

Hexagon bolt grade:

The grade of the external hexagon bolt is composed of two parts of numbers, which are used to represent the nominal tensile strength and yield ratio of the external hexagon bolt, respectively.

For example, the bolt of performance grade 4.6 has the following meanings:

a. The nominal tensile strength of the bolt material reaches 400MPa;

b. The yield ratio of bolt material is 0.6;

c. The nominal yield strength of the bolt material reaches 400 × 0.6 = 240MPa.

Performance grade 10.9 high-strength bolts, after heat treatment, the material can achieve:

a. The nominal tensile strength of the bolt material reaches 1000MPa;

b. The nominal yield strength of the bolt material reaches 1000 × 0.9 = 900MPa.