durable well drilling /mining 4 1/8" single roller bits

durable well drilling /mining 4 1/8" single roller bits Product Description IADC WOB(KN/mm) RPM(r/min) Applicable Formations 527 0.3-0.7 120-50 Soft formation with low compressive strength and high drillability,such as mudstone,gypsum,salt,soft shale,soft limestone,etc 547 0.3-0.7 100-50 Soft to medium formation with low compressive strength,such as medium soft shale,medium soft limestone,medium soft sandstone,medium for formation with harder and abrasiver interbeds,etc. 617