DRILLING BIT WHOSE DIAMETER IS ADJUSTABLE

摘要

PURPOSE: A drilling bit whose diameter is adjustable is provided in which diameter of the bit is freely adjusted without replacement of the bit during drilling operation of the inside of tap hole. CONSTITUTION: The drilling bit whose diameter is adjustable comprises a guiding main body(100) comprising a plural guiding projection parts(110) longitudinally formed on the outer side a conical shaped main body that is getting narrower as it goes from the front side to the rear side; a plural bit diameter adjusting guides(200) at both sides of which connection protrusions are formed, and which are slidingly moved along the outer inclination plane of the guiding main body with the connection protrusions being inserted into the guiding projection parts of the guiding main body; a drilling rod(300) connected to an end part of the guiding main body, and on the outer surface of which a plural resting grooves(310) are longitudinally formed with being spaced apart from each other in an equal distance; a quick coupler(400) which is hinge connected to an end part of the bit diameter adjusting guides inserted into the inner side of the quick coupler and installed at the outer side of an end part of the drilling rod in such a way that the quick coupler is attached to or detached from the drilling rod; and a plural drilling tips(500) connected to the front end of guide main bodies(210) in such a way that the drilling tips are attached to or detached from the guide main bodies.