Tightening of threaded fasteners—torque angle method

The torque angle method is to first tighten the hardware bolt to a certain fitting torque, and then tighten a certain angle (in order to facilitate manual control, the angle is usually a multiple of 60° or 90°) to control the total elongation of the bolt , So as to achieve the purpose of precise control of the axial force. Different from the torque method, the corresponding process parameters of the torque angle method can generally only be obtained through a special process test, and it is impossible to obtain it through calculation or table lookup. (Guide: Four major inspections for special quality of fasteners)

In addition, the torque angle method requires the use of expensive electric combination tightening machines with torque/angle control and monitoring functions and corresponding pre-development test equipment. The electric combination tightening machine can not only control the bolt tightening process, but also monitor the final tightening state of the bolts, and find some abnormalities of related threaded fasteners and clamped parts (thread interference, hairpin, high or low strength, Abnormal deformation, breakage, etc.) and give an alarm signal to facilitate the realization of full quality assurance. In view of its high technical requirements and high process cost, the torque angle method is usually only applied to important high-strength bolts such as engine connecting rod bolts. Using the torque angle method, the bolt can be tightened to within the elastic range, and the bolt can also be tightened to the plastic range.

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