415/425/435

Low   compressive strength, high drill-ability and extremely soft formation, like   shale, clay, sandstone, conglomerate etc.

 0.35~0.90

 140~70

447

Low   compressive strength, high drill-ability and soft formation, like shale,   clay, sandstone, soft limestone, salt rock, plaster etc.

 0.35~100

 140~60

517

Low   compressive strength, high drill-ability and soft formation, like   shale, clay, sandstone, soft limestone, salt rock, etc

 0.37~1.05

 120~50

527

Soft   formation with low compressive, like Low compressive strength, high   drill-ability and soft formation, like shale, clay, sandstone, soft   limestone, salt rock, anhydrite etc.

 0.37~1.05

 120~50

537/547

Low   compressive strength, medium hard formation with hard abrasive   interlayer, like Hard shale, anhydrite, soft limestone, sandstone,   dolomite with mezzanine, etc.

 0.50~1.05

 110~40

617/627

High   compressive strength, medium hard and thick hard interlayer, like hard shale,   limestone, sandstone, dolomite, etc.

 0.50~1.05

 80~40

637/647

High   compressive strength, medium hard and high abrasive formation, like   limestone, dolomite, sandstone, chert, etc.

0.7~1.20

70~40