... Besides, the PDC bits don't requires figuring, which lows the labour intensity and helps to saves cost. GE, American company, produces the ... 1.5 times of the ordinary bits, which has excellent abrasive resistance and applied to medium and hard rock (f≤12). 4 ... the ledge acts as cushioning to avoid huge drilling footage, which helps to low the possibility of damage. Thanks to that, the drilling level of ...