GB540027A - Improvements in and relating to rock boring and like tools - Google Patents

Abstract

540,027. Drills and cutters. COX, P. April 26, 1940, No. 7551. [Class 83 (iii)] In a counterboring tool, particularly for enlarging the inner ends of shot holes previously drilled in rock or the like for accommodating explosive charges, of the kind comprising a slotted body which is introduced into the hole and rotated therein and contains pivoted cutters mounted side by side and fed laterally into concounterboring poition by actuating means having thrust engagement with the bottom of the hole, guide abutment means are provided which contact along a lower portion of the side of each cutter to afford support against lateral thrust on the cutters when in the extended position in counterboring position by actuating means be attached at 2 to the means for rotating the tool, is provided with slots to receive an opposite pair of flat cutters 6, which are mounted in a pivot and have a curved portion and a straight portion accommodating tapered diamond mountings. The cutters are provided with oppositely inclined slots comprising curved portions 10 and straight portions 11 engaged by a common actuating pin 13 on a spring-controlled rod 17, which adjusts the cutters outwardly when the removable centre piece 18 on the rod is pressed against the bottom of the shot hole. The outward movement is limited by a pin 8 engaging a recess 7 in the cutter. Members 9 welded in position to occupy half the width of the slots in the body take lateral thrust on the cutters. Centre pieces 17 of different lengths may be used to vary the position of the counterbore, while the length of the counterbore is determined by the length of the straight part 11 of the cutter slot. In another form, Fig. 7, the removable centre 26 is secured in the tubular body 25, the outward movement of the cutter 28 being effected by a pair of toothed racks 34 carried by a spring-controlled member 32 moved relatively to the body and attached to the drill rotating means. The cutters are mounted in separate pivots 30 and are provided with, toothed sectors 29 engaging the racks. The racks occupy one half of the cutter slots and lie alongside the cutters to take lateral thrust. Shoulders on the racks engage the ends of arms 42 on a stop member 41 secured to the body when the cutters are in their withdrawn position. The outward position of the cutters is limited by the member 32 engaging the shoulder 35. on the body. The tools have vertical bores which extend into the cutter slots for the supply of washing liquid.