Three calculation methods for high-strength bolts

The pre-tension of the high-strength bolt is achieved by tightening the nut. Generally, torque method, angle method and torsion shear method are used.

(1), torque method. A special wrench that can directly display the torque is used to apply the torque according to the relationship between the torque measured in advance and the tension of the bolt to achieve the predetermined pretension. (Guide: Measures to improve the dispersibility of the fastener galvanizing solution)

(2), the corner method. There are two steps: the initial screwing and the final screwing. The initial tightening is to first use an ordinary wrench to make the connected components closely fit each other. The final tightening is to start from the initial tightening position, and rotate with a powerful wrench according to the final tightening angle determined by the bolt diameter and the thickness of the board When the nut is screwed to a predetermined angle value, the tension of the bolt reaches the required pretension value.

(3), torsion shear method. Twist off the plum head at the end of the bolt. First tighten the bolt, and then use the two sleeves of a special electric wrench to cover the nut and the torx end of the bolt. During operation, the large sleeve rotates forward to apply the tightening torque, and the small sleeve applies the tightening reverse torque. After the bolts are tightened, the torx head is unscrewed along the notch in the tail. Since the depth of the notch is determined according to the relationship between the final tightening torque and the pre-tension, the prescribed pre-tension value is reached when the torx head is unscrewed.

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