POINT ATTACK TOOLS: AN EVALUATION OF FUNCTION AND USE FOR ROCK CUTTING

Abstract

Point attack tools are being increasingly used as the cutting elements of roadheaders. The paper summarizes the results of recent research at the mining research and development establishment on their behaviour in cutting rock. For comparable cuts, sharp point attack tools require higher forces than sharp wedge-shaped tools. As both types become worn, the ranking order is reversed. For all tools, the deeper the cut the greater the efficiency. In laboratory tests point attack tools made more respirable dust and had a higher potential for producing methane ignitions. Point attack tools may wear better, this attribute being promoted if they rotate in the holders. The rotation produces uniform wear, not self-sharpening. Tip fracture potential is about the same for both point and wedge types. Point attack tools have value where resistance to abrasive wear is desirable, but a good depth of cut should be taken with them. In any projected use their environmental disadvantages should be considered. A theoretical analysis indicates that the same fundamental mode of rock breakage is invoked by both wedge and point attack tools. (a) (TRRL)