The carriage bolt is a very popular bolt now. In order to better apply this kind of equipment, we must select it reasonably in the selection process of the preload.

In the assembly of professional bolt fasteners, standard wrenches are generally equipped. Different diameters of bolts use wrenches of different lengths. The length of the wrench is about 15 times the diameter of the bolts. On this basis, professional mechanical tools can be used. It is particularly important for some key and important parts to reflect the accurate tightening torque and achieve a quantifiable preload. Once a large-sized long wrench is used to tighten a small-sized bolt, it will often cause over-tightening, destroying the part itself and causing the entire connection structure to fail.

When tightening the nut, two or more parts are compressed, and the parts themselves are compressed, just like the compression deformation of the spring, the parts themselves will generate a lot of force on the contact surface between the nut and the bolt and the assembly, this The force will cause tensile deformation of the bolt, which is calculated to be 1.3 times the simple axial tensile force,

When the tensile stress generated by the bolt exceeds the strength limit of the material, the bolt is pulled off. It is very unscientific for mass-produced products to tighten bolts only through the operator's experience. When tightening small bolts with a long wrench, more attention should be paid to the size of the pre-tightening force to avoid excessive pre-tightening.

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