... tooth life in more abrasive formations. Effective operating weights are from 1,000 to 3,000 pounds per ... the stresses imposed in drilling hard formations under heavy weights. The gage teeth are hard faced with tungsten ... The most economical bit performance is obtained with weights of 3,000 to 8,000 pounds per ... to drill most efficiently in hard formations with weights ranging from 3,000 to 8,000 pounds ...