... 2", 6-5/8" REG. GHJ series tri-cone rock bits with metal-sealing bearing system for oil well drilling.Main structure ... 0.35~0.90 KN/mm, Rotary speed, 300~60 r/m.2, Soft with low comprssive strength, such as shale ... 0.35~1.05 KN/mm, Rotary speed, 250~60 r/m.3, Medium soft with hard abrasive treak, such ... 0.5~1.05 KN/mm, Rotary speed, 200~40 r/m. ( function(){ var aBigImageSrc = [ 'http://i00.i.aliimg.com/ ...