Screw-in pile tip capable of being automatically contracted and expanded and reusable full-length drill rod

The invention relates to a screw-in type pile tip capable of being manually opened and automatically folded and a full-length drill rod applying the screw-in type pile tip, and belongs to the field of civil engineering. A screw-in pile tip capable of being automatically contracted and expanded is arranged at one end of a pile head and comprises a tip head and a rotary cutter. The pointed end is arranged on the center line of the pile head and serves as the head of a drill hole. The multiple rotary cutters are arranged around the pointed end, one end of each rotary cutter is rotationally connected with the end of the pile head, during drilling, the rotary cutters are unfolded outwards to be in a horizontal state, after drilling is completed, under the action of the pipe pile and upward pulling force, the rotary cutters are folded inwards, and the outer diameter of the folded rotary cutters is smaller than the inner diameter of the pipe pile. The method has the following advantages: 1, resource waste is avoided