IADC WOB(kM/mm)  (Bit Dia) RPM(r/min) Applicable Formations 512 0.35--0.7 120-60

Soft formations with low compressive strength and high drillability,such as mudstone,gypaum,salt,soft shale ,soft
limestone,etc.

542 0.4---0.8 100-60 Soft medium formations with low compressive strength ,such  as medium  soft shale, medium soft limestone,
medium soft sandstone ,medium fomation with harder
and abrasive interbeds,etc. 612 0.5---0.9 100-60 Medium hard formations with high compressive strength,
such as hard shale,limestone, sandstone,dolomite,etc. 732 0.6---1.1 90-50 Medium to high abrasive hard formations such as hard
shale, hard limestone, sandstone,siltstone, basalt,
granite,quarts sandstone,hard dolomite,hard limestone,
pynte,etc.