The hexagon bolt, hex head bolt thread) - C and hexagonal head bolt (full thread) - C level,, also known as hex head bolt (rough) hexagonal head bolt, black iron screw.

Hex bolt: the head and the screw (with external thread of the cylinder) of two parts of fasteners, to cooperate with nuts, used for fastening the two parts with hole.

This kind of connection form according to bolt connection. Such as screw the nut on the bolt, can make the two parts separately, so the bolt connection is a detachable connection.

The definition of A, B, C bolt aperture concept

Ordinary bolt and class A, class B (refined bolt) and C (unfinished bolts) two kinds

A and B grade bolts with 5.6 and 8.8 magnitude, steel grade C bolt with 4.6 and 4.8 magnitude steel. High strength bolts with 8.8 and 10.9 magnitude steel. 10.9 on the Richter scale in 10 said steel tensile strength limit for fu = 1000 n/was, said steel yield strength fy 0.9 = 0.9 fu, other models and so on. Anchor bolt used Q235 and Q345 steel.

Grade A, grade B bolts bolts (refined) composed of blank by rolling, bolt rod surface is smooth, size is accurate, screw holes need drill into the diamond, or on A single parts first blunt into smaller hole, and then on the assembly good components to design reaming aperture (called A type I hole). The diameter of the screw is very small, the gap between the aperture and allows only 0.3 mm or so, gently blow manholes during installation, as well as the shear and tensile. But grade A, grade B bolts bolts (refined), manufacture and installation of all the work, the price is expensive, only used in steel structure for the installation of important node, or under dynamic loading is both shear and tensile bolt connection.

Because c grade bolts (unfinished bolts) manufacturing is simple, cheap, convenient installation, is often used in various kinds of steel structure engineering, particularly suitable for bear along the screw axis direction tensile connection, detachable connection and temporary fixed member in connection with installation. As in connection with the larger shear action, considering the faults of the bolt and switch to bracket construction measures to withstand shear, let it pull force only to recognize the benefits of it.

Class C bolt can be used for dynamic loading under static load or indirectly secondary connections as shear connection.