STEP PROCESSING METHOD FOR DRILLING HOLE

摘要

PROBLEM TO BE SOLVED: To provide a step processing method for drilling hole that can solve a problem in which a conventional step processing method for drilling hole requires a bucket for drilling dedicated to a diameter expansion part and is thereby high in manufacture cost and construction cost and long in construction period.SOLUTION: A step processing device 1 for drilling hole is constituted which comprises: a rod suspended from a kelly-bar; a bucket for drilling provided at a lower end part of the rod; an expansion blade which is provided on the rod, and swings to be made compact within a diameter range of the bucket for drilling when stored, and projects and swings from the diameter range of the bucket for drilling when expanded to obliquely drill a step part of a hole wall through rotation of the kelly-bar; and a swing driving device provided on the rod so as to make the expansion blade swing. In a step processing device for drilling hole, the step processing device for drilling device 1 drills a step part formed in a drilling hole in a tapered shape with the enlargement blade 5.