... series tri-cone rock bits for well drilling: 1, Very soft with low compressive strength, such as soft marl, ... 0.35~0.90 KN/mm, Rotary speed, 300~60 r/m.2, Soft with low comprssive strength, such as ... Drilling weight:0.35~1.05 KN/mm, Rotary speed, 250~60 r/m.3, Medium soft with hard abrasive treak, ... Recommended Bit type: GHJ537, Drilling weight 0.5~1.05 KN/mm, Rotary speed, 200~40 r/m. ( function(){ var ...