... -1/2" ~ 12-1/4. 4, Connection: 4-1/2", 6-5/8" REG. GHJ series tri-cone rock bits with ... 4-1/2REG 42 9-12GHJ437T 437 9-1/2 6-5/8REG 60 9-1/2GHJ447T 447 9-1/2 ... 2GHJ51G 517 9-1/2 6-5/8REG 60 12-1/4GHJ437T 437 12-1/4 6-5/8REG 98 12-1 ... /4GHJ517T 517 12-1/4 6-5/8REG 98Drilling parameters of GHJ series tri-cone rock ... 1.05 KN/mm, Rotary speed, 200~40 r/m. GY series tri-cone bits for oil well drilling