To enhance frictional joining efficiency, and improve safety by giving a concentric circle-shaped recess-projection pattern to the peripheral edge of a bolt hole of a splice plate to sandwich a joining part of a steel structure such as a bridge from both surfaces, by knurling pieces.
A concentric circle-shaped recess-projection pattern with a bolt hole as the center is given to the peripheral edge of a bolt hole of a splice plate for frictional joining by a high strength bolt by rolling by knurling pieces, and hardness of a projecting part of the pattern is hardened by work hardening and quenching. When this recess-projection pattern is given, plural knurling pieces are installed in a symmetrical or regular polygon shape in a drill and a rod fixed to a rotary work machine such as a drilling machine, and rolling is performed. A depth of the recess-projection pattern is made deep in roughness or more of a surface given by a shot blast or the like, and a frictional coefficient is made large when it is fastened by a bolt. Therefore, reliability of a frictional joining part can be improved.
YOSHIE ATSUHIKO
KOBAYASHI SEIICHI
KOBAYASHI SEIMITSU KOGYO KK