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Selection of bolt tightening tools

April 17, 2024

The selection of bolt tightening tools should follow the following points:
(1) Process requires precision. At present, there are two main types of tightening workers: one is pneumatic tightening. Another type is electric tightening, the former has lower accuracy than the latter, and engine bolts are mostly tightened by electric tightening.

(2) The safety level of the connected components. When connecting bolts, it is necessary to ensure that the clamping force is higher than the external load, and a certain safety margin must be provided. The influence of bolt safety margin is affected by the vibration conditions of the connecting pair, changes in friction force, tightening accuracy, and changes in the size of the connecting parts. Generally, the optional safety margin is related to the tightening accuracy and material grade.

(3) Product material characteristics. It depends on the material of the connection and the object being connected, and is generally related to the ductility of the material. According to the measurement principle of clamping force, the better the ductility of the material, the greater the clamping force obtained.

(4) Space requirements. There are two types of electric tightening tools for tightening engine bolts: handheld and automatic. Handheld tools are relatively cheaper than automatic tightening tools. In the engine assembly process, depending on the installation method and human-machine engineering of different workstations, handheld tools are generally used for workstations with small space and fewer bolts, while automatic tightening generally requires workstations with large space and more bolts.

(5) Connection characteristics. There are two types: one is soft connections. After tightening to the fitting point, it is necessary to continue rotating for more than 2 turns to reach the target torque value. Another type is hard connection. After tightening to the fitting point, rotate within 30 degrees to reach the target torque value. Note: the fitting point is generally 10% of the target torque.

(6) Production efficiency, etc. The manifestation of efficiency is the tool failure rate and qualification rate. If the tightening tool failure rate is low and the qualification rate is high, then the production efficiency is high. Generally, it needs to be selected based on the product design value and the method to be monitored. After selection, corresponding MSA (Measurement System Analysis) analysis is carried out to ultimately determine whether the tightening tool meets the requirements of production efficiency.