... drilling and so on.3.It is almost suitable for hard rocks, such as limestone, dolomite, chert, firm sandstone, and firm anhydrite and so on.4 ... /8”)212.7mm(8 3/8”),215.9mm(8 1/2”),222.2mm8 3/4”) 241.3(9 1/2”),244.4(9 5/8”),250 ... 8”),349.2(13 3/4”)374.6(14 3/4”)381(15”),393.7(15 1/2”),406.4(16”)444.5(17 1/2”),508( ... 20”),558(22”),609.6(24”)660.4(26”) Steel tooth(IADC ...