Top Hammer Drilling Tools 7 11 12 degree quality taper steel 22mm x 108mm drilling rods for sale Tapered drill rod (taper steel rod, taper drill steel), which provides a hexagonal chuck section to provide leverage for the rotation chuck bushing. It usually has a forged collar to maintain the proper shank striking face position in the rock drill, and a tapered bit end. For drilling medium-hard to hard and abrasive rock formations, 11 and 12 taper degree rod are widely used on heavy-duty modern hydraulic drill rigs. While, 6 and 7 taper degree rod are applied for light-duty rock drill, such as the hand held pneumatic rock drill Y18, Y20, Y24, Y26, YT24 and YT28.