PURPOSE: To rapidly and accurately punch a charging hole for a strap bolt with the upper surface of a manufacturing material as a reference.

CONSTITUTION: An elevation base 9 which is vertically moved by elevating means 10 is provided at the rear side of a table 3 for placing a working material W. A drill head 12 having a long drill T is provided at the base 9, and longitudinally operated by protruding means 13. A vertical guide 14 is mounted at the base 9, and a contact piece 18 is so provided at the guide 14 as to be adjustable in height. The piece 18 is disposed at an upper side corresponding to the upper surface of the material W.