torquing

Torquing is the process of applying a specific torque to a fastener, such as a bolt or nut, to achieve the intended clamping force and joint integrity. It is a common procedure in automotive, mechanical, industrial, and aerospace applications, where incorrect tightening can compromise safety or performance. Torque is specified by the design or manufacturer and is usually measured in newton-meters (N·m) or foot-pounds (ft·lbf).

Tools and methods include torque wrenches of various types, such as mechanical beam, click-type, digital, and hydraulic models. Some assemblies use torque-to-yield or torque-plus-angle methods, where an initial torque is followed by a measured rotation. Proper torquing depends on correct thread condition, appropriate lubrication as specified, and the use of the correct fastener grade and thread engagement. Lubricants alter friction and thus the torque-tension relationship, so the specified torque may assume a particular lubrication state.

Procedure for multi-bolt joints typically involves a tightening sequence (often criss-cross or star patterns) and tightening in stages to the final specification. After final torque, recheck may be required if temperatures have changed or if the joint is critical.

Common issues include under-torquing, which can lead to loosening, and over-torquing, which can strip threads, stretch bolts, or cause failure. Other problems arise from cross-threading, contamination, incorrect lubricants, or damaged fasteners. Regular calibration and maintenance of torque tools are advised to ensure accuracy and repeatability.