... delivery 5.IADC 527 8 3/4" IADC 527 Kingdream drill bits for rocks HAS series for oil well 1.Introduction about us: Hejian ... , subterranean heat. Hydrology welling drilling and so on.3.It is almost suitable for hard rocks, such as limestone, dolomite, chert, ... 7/8”)212.7mm(8 3/8”),215.9mm(8 1/2”),222.2mm8 3/4”) 241.3(9 1/2”),244.4(9 5 ... 7/8”)269.8(10 5/8”),295.3(11 5/8”)311.1(12 1/4”),346.0 (13 5/8”),349 ...