For very soft formations:
Long intervals of very soft poorly compacted shales, sandstones, clays, salts and soft limestones.
Very long widely spaced, chisel-shaped inserts and considerable cone axis offset against centre line of bit to ensure very high penetration rate. The teeth have larger tip diameter. The design of teeth ensures higher penetration. To secure the bit from diameter loss, the gage protection inserts have got shorter length and greater angle of the top.
For Soft Formations:
Stratified soft rocks such as: lime clays, sandstones with lime binder, conglomerates, stratified soft and medium-compacted rocks, marbles, sandstones with clay-silica binder, Medium hard compacted rocks such as hard crystalline limestones, silica sandstones with ferruginous binder, etc.
High penetration rate is ensured by long chisel-shaped inserts and considerable offset of cone axis against the centre line of a bit. The teeth are spaced widely & unevenly. Greater top angle of the insert prevents from breakage and maintains full gage longer.
For Medium Formation:
Medium hard and abrasive rocks such as: sandstones with streaks of quartz, hard limestone, ferruginous or silica binder, crystalline dolomites, hematite ores, well-compacted abrasive rock such as sandstones with quartz binder, etc.
Short chisel-shaped or conical inserts closely spaced ensure effective penetration rate in the drilling of medium hard rocks as well as durability of the tool. Teeth height is set low to avoid tip damage. Heel row inserts are used to maintain full gage longer.
For Hard formations:
Hard, well-compacted rocks such as: hard silica limestones, quartz streaks, hematite ores, magnetite ores, chromium ores, granites etc.
A large number of short inserts with great top angle, closely spaced, ensure optimum condition for drilling in hard formation. Minimum cone axis offset against centre line of the bit prevents the inserts from breakage. The design shape of the main teeth ensures continuous crushing under typical drilling conditions.
A large number of heel row inserts maintain full gage longer.