... Rod body craft: friction welding, which improves the bending strength and the firmness of the drill rod. Production facility: CNC machining equipment, ... torque, quick slagging, and clear hole forming. Besides, the drill bit will hardly get stuck. Application: soft coal bed, and other ... coal seam, diameter 90mm, 113mm, 133mm, 146mm will be recommended. It will be more convenient to lay and install core ...