Drill bit shank from 0 to 7. The Morse taper allows the bit to be mounted directly into the spindle of a drill, lathe tailstock, or (with the use of adapters) into the spindle of milling machines. It is a self-locking (or "self holding") taper of approximately 5/8" per foot that allows the torque to be transferred to the drill bit by the friction between the taper shank and the socket. The tang at the end of the taper is only for ejecting the drill bit from the spindle, with the aid of a drift. The arbor of a drill chuck is often
Down-the-hole drill the drill rods working with a relatively large diameter drill bit caused bore holes to deviate which sometimes meant that a bore hole might finish dangerously close to its neighbour or indeed be closer to the face of the quarry than had been intended. In any event boreholes that are not aligned correctly which are then loaded with high explosive can be extremely dangerous, resulting in rock being projected beyond the intended site. Larger quarries used big rotary machines that required huge amounts of down thrust and high rotation speeds to drive the tri-cone bit hard enough to crush the