... " ~ 6-5/8" REG. GHJ series tri-cone rock bits with metal-sealing bearing system for oil well drilling ... 5/8REG 60 Drilling parameters of GHJ series tri-cone rock bits for well drilling: 1, Very soft with ... compressive strength, such as soft marl, clay, unconsolidated sandstorm, salt, etc. Recommended Bit type: 437, Drilling weight: 0.35 ... , 200~40 r/m. F/FC series tricone rock bits for oil well drilling