Tc hinge boring bits din 7483 g heavy duty hinge boring bit for precise drilling even in abrasive building materials the tungsten carbide hinge boring bit is designed for high performance and long life professional window door and kitchen fitters appreciate the particularly long life of these bits in abrasive materials such as plywood and hardwood chipboard fibre wood board and plastic laminated wood precision ground tungsten carbide blades 2 of each diamond ground side and main blade