... series tri-cone rock bits with metal-sealing bearing system for oil well drilling.Main structure features:1. This series ... Recommended Bit type: GHJ517, Drilling weight:0.35~1.05 KN/mm, Rotary speed, 250~60 r/m.3, ... etc. Recommended Bit type: GHJ537, Drilling weight 0.5~1.05 KN/mm, Rotary speed, 200~40 r/m. ( ... ); } )(); GHJ series tri-cone rock bits with metal-sealing system for oil well drilling