RAISE AND SHAFT DRILLING - A CONTINUOUS DEVELOPMENT.

Raise drilling (boring) today has become the standard method of raising in the western world. It is estimated that the majority of raise footage completed in 1977 was by the raise drill method. Some of these available machines are described and it is concluded that the possibility of new systems and designs should be re-assessed continually since the factors which determine their feasibility, such as bore diameter, cutter costs, and penetration rates, are changing rapidly.