The shape and connection structure of roof bolts are basically the same as those of ordinary bolts. The Cap Screw Factory will introduce the main difference between the two. Ordinary bolt connection relies on bearing pressure and shear resistance of the shaft to transmit shear force, and the pretension generated by bolts when tightening nuts is very small, so its influence will not be considered. The working principle of roof bolt connection is to intentionally apply a large pre-tension force to the bolt so as to generate extrusion force between the contact surfaces of the connected pieces, thus there is a large friction force perpendicular to the direction of the screw, and the connection shear force is transmitted by this friction force. The pretension of roof bolts is realized by tightening nuts. Common roof bolts generally adopt torque method and corner method. Torsional shear roof bolts use twist bolt tail to control pretension.
Bolts connected by Roofing Bolts are made of 10.9S or 8.8S grade high-quality alloy structural steel and heat treated. Holes for high-strength bolts shall be drilled. The nominal diameter D of the aperture ratio bolt of the high-strength bolt connected by friction type is 1.5-2.0 mm larger; The nominal diameter D of the aperture ratio bolt of the high-strength bolt connected under pressure is 1.0-1.5 mm larger.