Perforating apparatus for cylindrical workpiece, method for perforating cylindrical workpiece, method for manufacturing cylindrical product, and method for inspecting cylindrical workpiece

A perforating apparatus for a cylindrical workpiece, comprising:

• a cradle having a center and a groove extending longitudinally in one direction horizontally from one end to another end;
• a stopper provided at the one end of the groove;
• a drill disposed vertically above the groove in the cradle and the drill is movable at least in a vertical direction, with the drill having a drill bit that extends in the vertical direction;
• the cradle comprises a horizontal reference surface that extends along a horizontal plane that is perpendicular to the vertical direction in which the drill is movable, a vertical reference surface that extends along the center of the cradle in the vertical direction in which the drill is movable, and the groove has an inclined surface, which has a continuous slope, that is directly connected to each of the horizontal reference surface and the vertical reference surface along the center of the cradle, each of the horizontal reference surface, the vertical reference surface and the inclined surface of the groove extend from the one end to the other end of the cradle, the inclined surface of the groove is recessed below the horizontal reference surface;
• and
• a chuck having a pair of opposing grippers movable toward each other in a respective direction perpendicular to the direction in which the groove extends, and the pair of opposing grippers are movable symmetrically with respect to a rotation axis of the drill bit, with each of the grippers further having a pair of vertically symmetric inclined surfaces extending upwards and downwards forming a recess;
• wherein the cradle is movable, respectively, with each of the grippers;
• wherein an inclination of the inclined surface of the groove is less than an inclination of the vertically symmetric inclined surfaces of each of the pair of opposing grippers relative to the horizontal reference surface;
• wherein the horizontal reference surface extends towards the center of the cradle beyond each respective gripper of the pair of opposing grippers in a respective direction towards the vertical reference surface.