Self-Locking Head-Replaceable Hard Alloy Drill Bit

A self-locking head-replaceable hard alloy drill bit, comprising a cutter head and a cutter bar, in the view of the cutter head tip being upward, the upper part of the cutter head comprising a drill tip and a drilling body positioned below the drill tip, the cutter head (6) being disposed at the upper end of the cutter bar, a cylindrical handle being disposed at the lower part of the cutter head, the outer diameter of the drilling body of the cutter head being larger than that of the cylindrical handle, a vertical cylindrical handle holding slot or cylindrical handle holding hole being disposed at the upper end of the cutter bar, and the cylindrical handle being mounted in the cylindrical handle holding slot or cylindrical handle holding hole, characterized in that:

• at least two cutter head notches are formed on the drilling body of the cutter head, each of the cutter head notches is formed by intersecting a first cutter head contact face and a second cutter head contact face which are vertical or vertically oblique, the first cutter head contact faces are more close to the vertical central line of the drilling body than the second cutter head contact faces, the side edge of each first cutter head contact face distal to the corresponding second cutter head contact face is bended towards the vertical central line of the drilling body to form a cutter head ridge edge, the distance between each cutter head ridge edge and the vertical central line of the drilling body is greater than the radial sectional radius of the cylindrical handle, a vertical line segment exits in each first cutter head contact face, the distance between the vertical line segment and the vertical central line of the drilling body is shortest among all of the distances between the first cutter head contact faces and the vertical central line of the drilling body, at least two protrusions which protrude upward are disposed on the upper end surfaces of the cutter bar and have the same number as the cutter head notches, the inner surfaces of the protrusions are positioned on the outer side of the wall of the cylindrical handle holding slot or the cylindrical handle holding hole, and the protrusions have such a structure that during the process of assembling the cutter head and the cutter bar, the cutter head ridge edges are sequentially in non-contact fit, interference fit or non-interference fit with the inner surfaces of the protrusions, and after the assembly is completed, the first cutter head contact faces are in close contact with the inner surfaces of the protrusions, and the second cutter head contact faces are in close contact with the first lateral surfaces of the protrusions.