Image Number 8 for United States Patent #5735647.
A drilling apparatus for drilling a worn and/or damaged tap hole refractory liner sleeve from a tap hole nozzle of an oxygen blown steelmaking vessel, the apparatus including an elongated, hollow boom structure with an elongated drill shaft rotatably disposed within the boom structure, motor means for rotating the drill shaft and moving it in both directions within the boom structure, and a clamp means at the outer end of the boom structure adapted to attach the outer end of the boom structure to the tap hole nozzle in an accurate, axially aligned position. A drill bit for use with the above drilling apparatus comprises a plurality of conventional rock drill bits attached to a base plate equally spaced in a pair of concentric circular arrangement around an axis of the base plate.
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