Selecting the correct bit is critical for drilling efficiency and cost control. For soft to medium formations (clay, shale, or soft limestone), PDC (Polycrystalline Diamond Compact) bits are highly recommended due to their high shear efficiency. For hard rock or abrasive formations (granite, basalt, or quartz), Tricone bits with Tungsten Carbide Inserts (TCI) are the industry standard. If you are drilling through unconsolidated gravel, a Steel Tooth (Mill Tooth) Tricone bit offers a more economical solution. Always match the IADC code of the bit to your specific rock hardness to prevent premature wear.