Power head transition key bushing

The utility model relates to a power head transition key bushing, which comprises a transition bushing body. The upper end of the transition bushing body is provided with an upper end plate, the outer wall thereof is evenly provided with a plurality of outer keys matched with key slots on the inner wall of a power head, the inner wall thereof is provided with a plurality of inner keys matched with key bars on a drill stem and the lower end thereof is provided with a detachable connecting board. The power head transition key bushing transfers torque through the outer keys and the inner keys. When the drill stems of different outer diameters are to be replaced, the transition key bushing is dismantled as a whole and the transition key bushing matched with the outer diameter of the drill stem is installed, consequently the work requirement of the drill stems of different outer diameters is met. The utility model has the advantages of simple and practical structure, low cost, convenient dismantlement and installation and improved construction efficiency and can realize large variable diameter span.