The rotary drilling method of boring large diameter holes for the mining and construction industries has proven to be very cost effective. Raiseboring has gained worldwide acceptance as the preferred method for constructing ventilation and hoisting shafts, ore passes and hydroelectric penstocks. Tremendous amounts of torque and thrust from the drilling machine are transmitted to the cutting head, each individual member of the drill string playing a vital role in the success of the project. We have been involved in the design and development of the threaded connections, material specifications and manufacturing of raiseboring tools, since the first raiseboring machines were built in the 1960s.