... series tri-cone rock bits with metal-sealing bearing system for oil well drilling.Main structure features:1. ... sandstorm, salt, etc. Recommended Bit type: GHJ437, Drilling weight: 0.35~0.90 KN/mm, Rotary speed, 300 ... , sandstone, etc. Recommended Bit type: GHJ537, Drilling weight 0.5~1.05 KN/mm, Rotary speed, 200 ... } )(); GHJ series tri-cone rock bits with metal-sealing system for oil well drilling