... has a super long life. The useful life of the PDC bit is 4~5 times than the diamond bit, 10 times than ... . It can be used widely, more suitable for drilling in the stratum with hardness coefficient f<9. 6. It has a ... , hornfels, pegmatite, diabase, etc8~10grade, 30~35°Very hardhard granite, the british conglomerate, quartzite, hard slate, volcanic rocks, chert, basalt, etc11,12 ...