... This series adopts non-isometry teeth placement in combination with optimized teeth height and shape.2. Applying the ... rock bits for well drilling: 1, Very soft with low compressive strength, such as soft marl, clay, ... 90 KN/mm, Rotary speed, 300~60 r/m.2, Soft with low comprssive strength, such as shale, clay, ... KN/mm, Rotary speed, 250~60 r/m.3, Medium soft with hard abrasive treak, such as hard shale ...