What torque is required to fully tension a high-strength bolt?
Torque is an invalid measure for fully tensioned installation, unless it is calibrated. In 1951, the first RCSC Specification incorporated a table of standard torque values for the installation of fully tensioned high-strength bolts. However, depending upon the condition of the threads, it was demonstrated that the resulting installed tension varied by as much as plus or minus 40 percent. It is now known that clean, well lubricated threads result in tensions that are higher than required (and probably a few broken bolts), whereas, rusted, dirty, or poorly lubricated threads result in tensions that are below the minimum required. Therefore, recognition of these standard torque values has long been withdrawn. Accepted procedures for fully tensioning high-strength bolts can be found in the 2004 RCSC Specification Section 8.2 (see also 6.6.3.). If torque is to be used as in the calibrated wrench method as described in the 2004 RCSC Specification Section 8.2.2, it must be calibrated on a da
