... bit, tungsten carbide insert rock bit, tri-cone drill bit , 3 cone bits, rotary bit, TCI ... tricone bit, PDC drill bit , diamond core bit, bicenter bit, single cone ... King Dream, CS, Lilin,Drag bits, which is designed for soft formations such as sand,clay,or some soft ... etc.Whenever possible,they should be used to drill pilot holes because they produce cutting that are ...