Drilling constitutes an important part of the production process in sublevel stoping method and up to 50% of the total costs can be attributed to this element. With the advent of recently developed sophisticated and expensive drilling machines, sublevel stoping has gained renewed advantage over other similar methods. The use of these machines, however, substantially increases the capital cost of the whole operation and hence choosing the optimum drilling system can produce significant savings in costs. In this paper, drilling patterns have been designed for various conditions of the physical characteristics and geometrical conditions of an ore body. Total costs of some 150 different patterns have been compiled. Based on these empirical data, a practical model has been devised that determines drilling costs in all different feasible situations in sublevel stoping. The model shows that parallel drilling is the most efficient alternative in all workable conditions. As well the break-even orebody thickness in ring drilling between one or two production drifts in sublevels is, in most cases, about 30 meters. The prescribed drilling methods in different circumstances and the model introduced, can serve as useful tools to the mining design engineer in choosing the most economical drilling system when designing a stope
