Wob(kn/mm)

Rpm(r/min)

116 117

0.35-0.8

150-80

Low compressive strength extremely soft   formation of high drillability, such as clay, mudstone, chalk

126 127

0.35-0.9

150-70

Low compressive strength soft formation of   high drillability, such as Mudstone, gypsum, salt rock, soft shale, soft   limestone

136 137

0.35-1.0

120-50

Low compressive strength soft to medium   soft formation of high drillability such as anhydrite, soft shale, medium   soft limestone, medium soft sandstone soft formations interlayer

216 217

0.4-1.0

100-50

High compressive strength medium soft   formations , such as soft shale, anhydrite, soft limestone, medium soft sandstone   and has a  interlayer

246 247

0.4-1.0

80-50

High compressive strength medium hard   formations such as abrasive shale, limestone, sandstone, dolomite and   anhydrite, marble

417 437   447

0.35-0.9

150-70

Low compressive strength and high drill   ability of extremely soft stratum, such as clay, shale, gypsum and halite,   soft shale, soft limestone

517 527

0.35-1.0

140-50

Low compressive  soft formations , such as mudstone, gypsum,   salt rock, soft shale, soft limestone

537 547

0.45-1.0

120-50

Low compressive strength of soft to medium   formation, Soft shale, medium soft limestone, medium soft sandstone, and   there are hard abrasive sandwich middle stratum

617 627

0.45-1.1

90-50

High compressive strength of medium hard   formations, such as sandstone, limestone, dolomite, hard shale

637

0.5-1.2

80-40

High compressive strength of hard   formations, such as sandstone, limestone, dolomite and anhydrite, marble