... its hardening resistance. 3. The roller bit uses new type lubricating grease which can bear the high ... smaller than bit. The roller bit is mainly used to scrape broken rocks, suitable for various small- ... it has extensive application fields. It can be used not only in well sidetracking but also in medium ... 1/2444.5517, 537, 617, 627, 637 Both new and used are available , we are purchasing all kinds of ...