DEEP HOLE DRILLING DEVICE

PROBLEM TO BE SOLVED: To provide a deep hole drilling device to which both a BTA drill method and an ejector drill method can be applied by the same device. SOLUTION: A deep hole drilling device is provided with a double tube 12 having a drill head 11 on the tip, a sending part 14 to send the doble tube toward a work 3 and a pressurizing part 16 to supply cutting oil to the periphery of the double tube by adjoining the work. The pressurizing part 16 is provided with an annular sealing bush 15 to seal its space by being pressed to the work in its front part. The sending part 14 is provided with a cutting oil supply part 20 which supplies a part of the cutting oil to an outside passage of the double tube in its front part and simutaneously flows the remiander of a supply liquid to an inside passage of the double tube. The cutting oil supply part 20 is provided with an ejector function to put the inside passage under negative pressure by the flow to the inside passage of the double tube, and is also provided with a cutting oil supply pump 22 to supply the cutting oil and a directional control valve 24 to selectively supply the cutting oil to the sending part or the pressurizing part from the pump, and a BTA drill method and an ejector drill method are switched to/from each other by this directional control valve.