What is the recommended action before torquing the nut on a high tensile bolt connection?

Before torquing the nut on a high tensile bolt connection, lubricating the threads is critical. Proper lubrication reduces friction between the nut and the bolt, leading to a more accurate torque reading and ensuring that the bolt is tightened to the correct specification. Lubrication also minimizes the risk of galling or binding, which can occur during the tightening process. This is especially important in high tensile applications where bolts are expected to withstand significant loads and stresses.

If the threads are not lubricated, the friction can significantly impact the torque applied, leading to an under-tightened connection that may not perform as intended, or an over-tightened connection that may cause the bolt to stretch beyond its limits. Therefore, lubrication is an essential step in the installation process, ensuring the integrity and reliability of the bolted connection.