Quadrangular with Deep Twist has an axial force is small, the chip large space, to drill cuttings back fewer, one feed can be drilled (10-20) d0 (d0 drill bit diameter) hole, guide reliable, row crumbs and smooth, coolant through the cooling fluid can enter the trough of the cutting edge portion, the cooling effect, drill high durability, good quality drilling a series of advantages.
Structural features 1. quadrangular with deep twist
　　(1) live cutting edge of the blade radial rake angle drill blades are substantially equal on points cut is positive, thus drilling conditions have improved. At the same time, the radial edge in favor of the use of planar flank, simplifying the drill grinding method
　　(2) large web thickness, the thickness k = (0.26-0.35) d0 (d0 drill bit diameter), and from the drill head to tail without increment. Enhanced strength and rigidity drill, and facilitate chip discharge
　　(3) the larger helix angle, β = 370. Increasing the drilling edge feed rake Υf, so that light cutting, Chip smooth, deep hole drilling favor.
　　(4) distribution has four circumferential ribs with the drill bit. Drilling is cutting edge and want to stay connected with two ribs, the secondary cutting edge is only a starting role, the other edge band play damping effect. The remaining two cold strip serves as a guide, so that formed three point circle, play a stabilizing role in the drilling.
　　(5) There are two open edges back arc spiral groove. Formed between the wall of the spiral grooves and holes to assist in infusion channel, can fully lubricate four corners of the band, and successfully entered the coolant to the cutting area, better cooling effect. Special repair mode diameter blade portion households, this trough may be its reaming chip flutes role.
　　(6) Special chip flutes, the chip large space. Depending on requirements, the chip flutes can be designed into two symmetric and asymmetric type. Symmetrical chip flute, 1 edge groove width dimension, the blade back and edge groove width ratio of: (2.5-4), and thus the chip large space. Such a wide edge ditch, although drill torsional rigidity has been weakened, but the chip smooth, reasonable edge shape. Centering good, thus greatly reducing the bit torsional stiffness requirements. Asymmetric type of chip pockets, how much metal is removed in accordance with two cutting edges, designed to be one small chip space of two chip pockets, so you can meet the requirements of large chip space, and a guest to increase drill horizontal cross-sectional area, increase drill torsional rigidity while reducing terrible grinding margin, simplify sharpening methods.