Tungsten Carbide Bits at the Britannia Mine

Abstract The Britannia Mining and Smelting Company, Limited, have replaced diamond drills with percussion drills and tungsten: carbide bits for most of their blast hole drilling operations and have thereby reduced ore breaking costs. Two-inch Carset bits .are used, with one-inch hexagonal Atlas Chippewa alloy steel in 3-foot .and 6-foot lengths. Locally made couplings of Atlas SPS 245 alloy steel connect the rods. The machines used are 31½-inch automatic leyners with lugged or anvil block chucks. For drilling holes below the horizontal, the lugged machines with special adapter rods made from 114- inch solid round Atlas SPS 245 are required. These rods are lugged at one end and a water hole is drilled for six inches into the other end. Over this rod is placed a water swivel which permits the water or air to be sent directly into the steel. A decreased cost per foot, increased footage per shift, and the use of standard equipment and crews are some of the main advantages of tungsten carbide drilling over diamond drilling. Introduction Long-hole drilling with percussion drills and sectional steel was introduced in several American mines some twenty-five years ago. It did not prove very successful, however, because the rapid gauge loss in steel bits necessitated the use of very large starter bits. This in turn rapidly fatigued the straight carbon-steel then in use, made it difficult to maintain the couplings, and resulted in a slow drilling rate. The introduction of the tungsten carbide insert bit and alloy drill still has changed this picture and opened real possibilities for the application of percussion drills to blast-hole drilling. If this type of bit had been perfected ten years ago, much of the research work and experimenting done to apply diamond drills to ore breaking would have gone toward developing the application of the tungsten carbide bit to this problem.