STANDARD BOLT TORQUE SPECIFICATIONS HOW TO DETERMINE BOLT STRENGTH Hexagon head bolt [Diagram of hexagon bolt with "4" marking] Mark Class 4- 4T 5- 5T Bolt head No. 6- 6T 7- 7T 8- 8T 9- 9T 10- 10T 11- 11T [Diagram of hexagon bolt] No mark 4T Hexagon flange bolt w/ washer hexagon bolt [Diagram of hexagon flange bolt] No mark 4T Hexagon head bolt [Diagram of hexagon bolt with two protruding lines] Two protruding lines 5T Hexagon flange bolt w/ washer hexagon bolt [Diagram of hexagon flange bolt with two protruding lines] Two protruding lines 6T Hexagon head bolt [Diagram of hexagon bolt with three protruding lines] Three protruding lines 7T Hexagon head bolt [Diagram of hexagon bolt with four protruding lines] Four protruding lines 8T Stud bolt [Diagram of stud bolt] No mark 4T [Diagram of grooved stud bolt] Grooved 6T Welded bolt [Diagram of welded bolt] 4T