Torque & preload table

Reading the table

K is the whole story. The same torque on a dry galvanized bolt and an oiled black bolt gives preloads that differ by nearly two to one. If preload matters — slip-critical joints, gasketed flanges, fatigue-loaded connections — specify the tightening method (turn-of-nut, DTI washers, tensioning), not just a torque figure.

Never exceed 85–90% of proof by torque alone; the scatter can take you past yield. Do not re-torque hot-dip galvanized or zinc-flake fasteners after relaxation without checking the coating has not been damaged. Class 12.9 and A490M are not for torque wrenches on site without a written procedure.