A shaft drilling rig comprises a rig head having means whereby it may be attached to a cable so as to be raised and lowered within a shaft being sunk. A central hollow column depends from the rig head and carries a base member at its lower end. There are rig supporting feet carried by the base member. The rig has a plurality of booms each being operatively carried at its upper end by the central column near the rig head to pivot relative to the column and itself carrying at its outer end a feed holder for a beam to carry a rock drill. A plurality of support members are respectively associated with the booms, each such support member being operatively carried at its lower end by the central column near the base member to pivot relative to the column and pivotally engaging its associated boom at a pivot location. Each boom has an extendable section arranged to extend the length thereof which extendable section is located between the upper end of the boom and its said pivot location. The central column slidably carries within it a sub-assembly having at its lower end a down-the-hole hammer, rotary means for rotating the hammer, and guide means for guiding the sub-assembly within the column. There is further provided a sprocket and chain device for moving the sub-assembly relative to the column. Thus the hammer can drill a central relief hole in the floor of the shaft being sunk before the blasting takes place in the holes drilled or to be drilled by the rock drills that will be carried by the mounting heads.
