... 6-5/8" REG. GHJ series tri-cone rock bits with metal-sealing bearing system for oil well ... 8REG 60 Drilling parameters of GHJ series tri-cone rock bits for well drilling: 1, Very soft with ... soft marl, clay, unconsolidated sandstorm, salt, etc. Recommended Bit type: 437, Drilling weight: 0.35~0.90 KN ... Bit type: 537, Drilling weight 0.35~1.05 KN/mm, Rotary speed, 200~40 r/m. F/FC series tricone rock ...