SEMS are bolts, which are called bolts with a dodecagon at the end. The main feature of these screws is they are equipped with corresponding washers, which are convenient to use. The biggest advantage is that can saves time and does not require any manual adjustment of the flat pad, which can make the production line easy, and quickly improve work efficiency.

The high-strength combination bolts are mainly applied on railway, highway bridges, boiler steel structures, industrial plants, high-rise civil buildings, tower mast structures, crane machines, and automobile engines. The steel structure requires high-strength friction-type bolts.

The characteristics of the friction-type bolts:

  • At the end of the bolt is a dodecagon, and need to used a special electric wrench to install it.
  • Two socket heads on the top and bottom. One is sleeved on the hexagon of the nut and the other is sleeved on the decagon of the outer hexagonal screw.
  • Torsion-shear type high-strength hexagonal screw is a one-time screw, and generally cannot be removed after installation.

When tightening, apply a clockwise torque to the nut and apply an equal and counterclockwise torque to the dodecagon of the bolt so that the end of the hexagonal screw and the neck of the dodecagon are subjected to torsion shear to the neck after installation.