A tension control bolt is a pre-assembled bolt, nut, and washer used especially in steel frame construction. Also known as a TC bolt, they possess a domed head rather than a hex head because they are installed from a spline on their other end. This spline connects with a special power wrench for installation. Other names for this fastener set-up include twist-off bolts and LeJeune bolts.

Tension control bolts come perfectly pre-lubricated by the manufacturer. They are ready to be installed with a shear wrench. This wrench has an inner and an outer socket. The inner socket rotates the spline clockwise and the outer socket rotates the nut counterclockwise. Once the correct tension has been achieved, the spline breaks off.

TC bolts install easier than heavy hex bolts, DTIs (direct tension indicators), and other construction fasteners.  There is just one lot number involved in the tension control bolt assembly and they come precisely lubricated.  They are regulated by the AISC, American Institute of Steel Construction, and RCSC, Research Council on Structural Connections. 

The single most unique feature of the tension control bolt is that it is installed with a precisely calibrated shear wrench that takes the guesswork out of achieving the correct preload (tension created in a fastener when it is tightened). This wrench connects over the spline of the bolt and once the correct tension has been reached, the spline breaks off.

Many feel that tension control bolts are more economical because they require only one person for their installation and inspection. Therefore, installation goes faster and with fewer mistakes.