... for oil well drilling.Main structure features:1. This series adopts non-isometry teeth placement in combination with optimized teeth height and ... KN/mm, Rotary speed, 300~60 r/m.2, Soft with low comprssive strength, such as shale, ... /mm, Rotary speed, 250~60 r/m.3, Medium soft with hard abrasive treak, such as hard ... .5~1.05 KN/mm, Rotary speed, 200~40 r/m. ( function(){ var aBigImageSrc = [ 'http://i00 ...