... carbide drag bit manufacturers,Website:http://www.tydrillbits.com, welcome to wholesale cheap carbide drag bit from our factory.The Drag Bits ... stiff clays and Mudstones very quickly. Usually used for construction or other site investigation projects. It has two types, Step ... degassing hole, drain hole,and grouting hole of coal mine. Or used for the purpose of geology, coalfield, metallurgy, building, ...