... REG. GHJ series tri-cone rock bits with metal-sealing bearing system for oil well drilling.Main structure features:1 ... more efficient, and more suitable for drilling at high rotary speed and high tem-perature working condition.3. ... 0.35~0.90 KN/mm, Rotary speed, 300~60 r/m.2, Soft with low comprssive strength, such as ... ~1.05 KN/mm, Rotary speed, 250~60 r/m.3, Medium soft with hard abrasive treak, such ...