How do you measure torque?

Common methods for measuring torque include various techniques, suitable for different scenarios and requirements. The tightening method (incremental tightening method) involves applying force smoothly in the tightening direction using a torque wrench until the bolt begins to rotate slightly, then recording the instantaneous torque value. This method is simple to operate but requires experience to determine the initiation point, and results may be slightly higher. The marking method requires drawing alignment marks on both the bolt and connected component to indicate the original position. After loosening, the bolt is retightened to the marked position, and the torque value is read and multiplied by 0.9-1.1 to obtain the result. While relatively accurate, this method is somewhat cumbersome and unsuitable for fasteners with anti-loosening features. The loosening method applies torque in the unscrewing direction, recording the initial movement torque value which is then multiplied by 1.1-1.2. Though simple to perform, results may be slightly low. Additionally, the re-tightening torque method involves turning an already tightened bolt through a small angle (not exceeding 15 degrees) and recording the breakaway torque. This non-destructive method offers strong reliability and is suitable for quality inspection during assembly. The verification torque method tightens to 80-90% of the specified torque - if no movement occurs, the connection passes inspection, making it ideal for pre-coated threadlocker applications. The residual torque method first loosens by 10-30 degrees before retightening to the original position, particularly effective for bolts where static friction significantly exceeds dynamic friction. Common tools include torque wrenches (available in dial and digital types, with digital offering higher precision) and digital torque testers, all requiring calibration prior to use to ensure measurement accuracy. Each method has distinct advantages and should be selected based on connection type (hard or soft joint) and anti-loosening features. For instance, when applying the re-tightening torque method to hard joints, the acceptable range is 0.8-1.2 times the specified torque, while soft joints allow 0.5-1.2 times. The marking method suits disassembly scenarios, whereas the verification torque method is appropriate for quality assurance of threadlocker-treated connections.