What is the pre-tightening torque of the bolt?

The material grade is 8.8, and the tightening torque is 259Nm.

Material grade 10.9, tightening torque 369Nm, material grade 12.9, tightening torque 432Nm, M20 material grade 6.8, tightening torque 262Nm, material grade 8.8, tightening torque 363Nm, material grade 10.9 and tightening torque 56544.

Metric bolt tightening torque Q/STB12.521.5-2000 This standard is applicable to bolts with mechanical properties of 10.9 and specifications from M6 to M39, but it is not applicable to bolts with nylon washers, sealing washers and other nonmetallic washers.

Extended data:

Precautions:

As an important connector, bolts must be tightened during assembly. Before the connector bears the working load, it is prestressed. This prestress is the pre-tightening force. The purpose of pre-tightening is to enhance the reliability and tightness of the connection and prevent the assembly and installation from being stressed during work, and there is a gap or relative sliding between the connectors. Therefore, the pre-tightening force must be standardized in the design of components.

In professional bolt fastening assembly, standard wrenches are generally equipped, and wrenches with different lengths are used for bolts with different diameters and specifications, and the length of the wrench is about 15 times of the bolt diameter. On this basis, the use of professional mechanical tools can reflect the accurate tightening torque and achieve quantitative pre-tightening, which is particularly important for some key and important parts.

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