Large hexagon head bolts refer to the size of the hexagon head is larger than ordinary hexagon head bolts; twisted shear high strength bolts can be said to be an improved version of large hexagon high strength bolts, construction is more convenient. The common point of these two kinds of high strength bolts for steel structure is single use, for permanent connection, can not be reused.

From the appearance, the head of the large hexagon head high strength bolts is positive hexagonal, twisted shear type high strength bolts have plum blossom head at the top.

From the construction method, large hexagonal head high strength bolts need to use constant torque wrench construction, screwing without holding wrapped screw, in the rotation of the nut may drive the screw 'with the turn', which requires the use of ordinary wrenches temporarily fixed large hexagonal head to avoid this phenomenon, to ensure that the effect of tightening; torsion shear high strength bolts to be used to torque shear type Twist-shear type high strength bolts should be installed with twist-shear type wrenches, and the screw itself should be clamped at the tail end with positive and negative twisted rods directly through the 'plum blossom head', so that the phenomenon of simultaneous rotation will not occur.

From the strength level, large hexagonal head high-strength bolts belong to the high-strength level of ordinary screws; torque shear high-strength bolts are improved for better construction of high-strength bolts, need to be tightened first after the final tightening of the initial tightening to be used with impact electric wrenches or torque-adjustable electric wrenches.

Large hexagon head bolts conventional test items are: bolt wedge load, nut guarantee load, connecting vice fastening axial force, nut hardness, washer hardness, bolt in-kind wedge load test, connecting fastening axial force, ultrasonic flaw detection, core hardness test, tensile load, bolt in-kind wedge load test.