tapers for smaller diameter bits and or raise machine with smaller capacities a smaller amount of make up torque on the preload nut 20 would be required for larger diameter bits and or raise machines with larger capacities the make up torque on the preload nut 20 would probably remain at 100 000 ft lbs the additional torque would be carried with the mechanical keys 22 23 27 and 28 between the friction faces of the preload nut 20 and its seat or a combination of the two the additional thrust would be carried in the threaded connection 15 of the stem 10 and preload nut 20 the structural details of a raise bit constructed in accordance with the present invention having been described a raise drilling operation will now be considered using the bit shown in fig1 the raise drilling operation begins by drilling a small diameter pilot hole through the earth from a first location to an opening at a second location using a small diameter pilot bit after the pilot hole is completed the pilot bit is removed from the drill column and the raise bit shown in fig1 is attached to the drill column the raise bit is rotated and drawn along the pilot hole thereby enlarging the pilot hole to the desired size the raise bit may be transported through small drifts or passages by removing the drive stem 10 and transporting the drive stem 10 and raise bit.