Abstract: An articulated boom arm for a rock boring machine, comprising a first kinked member having a drill guide at one end and a base pivot at the other end, and a pair of pivoted links. One of said links having a first end pivoted at said base pivot, the other of the links having a drill pivotally mounted at a first end thereof. The second ends of The first and second links being pivoted to each other whereby said drill is reciprocally linearly movable along said first member with a drill bit aligned with said drill guide and at one extremity of the reciprocal movement both said pair of links are substantially longitudinally aligned and extend towards said drill guide, and at the other extremity of the reciprocal movement both said pair of links are substantially longitudinally aligned and extend away from said drill guide.