Bolt, with nuts cylindrical threaded fasteners. Is a machine part, usually fixed in the periphery of the mechanical equipment, bolt by the head and the screw (with external thread of the cylinder) of two parts of fasteners, to cooperate with nut, used for fastening the two parts with hole. And, have greatly small,what size bolts, of course also cannot be determined, in accordance with the relevant standards, bolt performance are rated 3.6, 4.6, 3.6, 4.6, 6.8, 8.8, 9.8, 10.9, 12.9, and so on more than 10 levels, including a magnitude of 8.8 and above the bolt is made of low carbon alloy steel and medium carbon steel and the heat treatment (quenching and tempering), known as high strength bolts, the rest of the known as ordinary bolts. Bolt performance rating label consists of two parts Numbers respectively represent the nominal tensile strength value of bolt material and QuJiang ratio. On the basis of the level below with specific examples to illustrate what size bolts, because you know the size of the class, will be able to calculate the size.
For example: performance level 4.6 bolt, its meaning is: bolt material nominal tensile strength of 400 mpa grade; Bolt material QuJiang ratio is 0.6; Bolt material nominal yield strength of 400 * 0.6 = 400 mpa. Performance grade 10.9 high strength bolt, its material after heat treatment, can achieve: bolt material nominal tensile strength of 1000 mpa grade; Bolt material QuJiang ratio is 0.9; Bolt material the nominal yield strength of 1000 * 0.9 = 900 mpa grade bolts performance level is the meaning of international standards, the same level of performance of bolt, regardless of its material and the origin of the difference, its performance is the same, the design can only choose performance level. Strength grade 8.8 and 10.9 magnitude refers to the level of the shearing stress of bolt is 8.8 GPa and GP, 10.9 magnitude 8.8 nominal tensile strength of 800 n / 640 n was nominal yield strength bolts/was generally is expressed in "X.Y" strength, X * 100 = the bolt tensile strength, X * 100 * (Y / 10) = yield strength of the bolt (as stipulated in the logo: yield strength tensile strength = Y / 10) such as magnitude 4.8, the tensile strength of the bolt is: 400 mpa yield strength for: 400 * 8/10 = 400 mpa, in fact, there are some data need to view the data through the form, and these data is the standard provisions of the state. Through the data view, in specific formula, can figure out what size bolts. Although cumbersome, but very accurate. Hope to help you.