The invention discloses a
twist drill for
machining holes of laminated welded steel. The
twist drill for
machining holes of the laminated welded steel includes a
cutting part and a shank part. The
cutting part includes a
drill tip and a secondary
cutting part, and the
drill tip is provided with two main cutting edges and a
chisel edge connecting the two main cutting edges. The secondary cutting part is provided with two
chip discharging grooves and two first cutting edge belts, and the first cutting edge belts and the
chip discharging grooves intersect to form a secondary cutting edge. The main cutting edges are provided with negative chamfers, and the negative chamfers do not pass the intersections of the main cutting edges and the
chisel edge. The length of the
chisel edge is L5, whereinthe L5 is larger than or equal to 0.017D and less than or equal to 0.03D, and D is the
diameter of the cutting part. According to the
twist drill for hole
machining of the laminated welded steel, thelength of the chisel edge is only one third of that of a conventional chisel edge, the length of the chisel edge of the
drill tip is small, the centering capacity during drilling of the laminated welded steel is increased, the twist drill for hole machining of the laminated welded steel is suitable for drilling machining of steel with varying
hardness among different materials, the problem of drilling deviation in the drilling process is reduced, the negative chamfers are arranged on the main cutting edge, no negative chamfer is arranged on the entire chisel edge, and the sharpness of the chisel edge is not changed while the strength of the main cutting edge is increased, so that the centering performance of the chisel edge is better.