... This series adopts non-isometry teeth placement in combination with optimized teeth height and shape.2. Applying the ... high rotary speed and high tem-perature working condition.3. New materl is applied on the part ... rock bits for well drilling: 1, Very soft with low compressive strength, such as soft marl, clay, ... Rotary speed, 250~60 r/m.3, Medium soft with hard abrasive treak, such as hard shale, soft ...