... -1/2GY437F 437 9-1/2 6-5/8REG 60 9-1/2GY517FC 517 9-1/2 6-5 ... -1/2GY517FT 517 9-1/2 6-5/8REG 60 Drilling parameters of GHJ series tri-cone rock bits ... 0.35~0.90 KN/mm, Rotary speed, 240~60 r/m.2, Soft with low comprssive strength, such as ... :0.35~1.05 KN/mm, Rotary speed, 220~60 r/m.3, Medium soft with hard abrasive treak, such ... 35~1.05 KN/mm, Rotary speed, 200~40 r/m. F/FC series tricone rock bits for oil ...