... is common diamond bit of 4 ~ 5 times;2, high drilling efficiency: diamond exposed big (composite polycrystalline layer almost all exposed ... greatly improve the penetration rate;3, low pressure, low speed drilling: bit to scart, shear to broken rock, the drill ... formation, the effect is particularly significant.Advantages of Rotary PDC Drilling Drag Bit 1.Quickly drill speed , long service life 2 ...