Self-locking head-replaceable carbide drill

A self-locking head-replaceable carbide drill, comprising a cutter head (6) and a cutter shank (12), in the view of a tip of the cutter head (6) being upward, an upper part of the cutter head (6) comprising a drill tip (7) and a drilling body positioned below the drill tip (7), the cutter head (6) being disposed at an upper side (19) of the cutter shank (12), a cylinder (1) being disposed at a lower part of the cutter head (6), the outer diameter of the drilling body of the cutter head (6) being larger than that of the cylinder (1), a vertical cylinder holding slot (14) or an cylinder holding hole being disposed at the upper side (19) of the cutter shank (12), and the cylinder (1) being mounted in the vertical cylinder holding slot (14) or the cylinder holding hole, characterized in that:

• at least two cutter head notches (9) are formed on the drilling body of the cutter head (6), each of the cutter head notches (9) is formed by intersecting a first cutter head contact face (5) and a second cutter head contact face (4) which are vertical or vertically oblique, the first cutter head contact faces (5) are more close to an vertical central line of the drilling body than the second cutter head contact faces (4), an side edge of each first cutter head contact face (5) distal to the corresponding second cutter head contact face (4) is bended towards the vertical central line of the drilling body to form a cutter head ridge edge (10), a first distance between each cutter head ridge edge (10) and the vertical central line of the drilling body is greater than an radial sectional radius of the cylinder (1), a vertical line segment exists in each first cutter head contact face (5), a second distance between the vertical line segment and the vertical central line of the drilling body is shortest between the first cutter head contact faces (5) and the vertical central line of the drilling body, at least two protrusions (17) which protrude upward are disposed on upper end surfaces (20) of the cutter shank (12) and correspond to each of the cutter head notches (9), inner surfaces (16) of the protrusions are positioned on outer sides of walls of the vertical cylinder holding slot (14) or the cylinder holding hole, and the protrusions have a structure that during the process of assembling the cutter head (6) and the cutter shank (12), the cutter head ridge edges (10) are sequentially in non-contact fit, interference fit, and non-interference fit with the inner surfaces (16) of the protrusions (17), and after the assembly is completed, the first cutter head contact faces (5) are in close contact with the inner surfaces (16) of the protrusions (17), and the second cutter head contact faces (4) are in close contact with first lateral surfaces (21) of the protrusions (17).