The following report investigates the drilling activity at two limestone Quarries belonging to Stevin Rock in Ras Al Khaimah, UAE. Quarry 2 (Q2) is located in Khor Khuwair and Quarry 3 (Q3) in the Al Ghail area where the limestone is denser and harder to drill. The objective of this project was to identify areas where the performance of the machines could be improved and the rock tools cost reduced. The drilling fleets, consisting of four machines at each site, were studied between January and June 2010 and the operational data recorded. The machines were observed and adjusted to improve their drilling performance. The sites were then compared on the basis of machine availability, utilization, production and drilling consumables cost. It was found that the mechanical availability of the machines were 74% and 69% at Q2 and Q3 respectively. The utilization at Q2 was 50% compared to 43% at Q3, which was low in both cases but sufficient to meet the drilling requirements. The average monthly drilling at Q2 was 23,611m with the four top-hammer machines in operation there. At Q3 the average was 22,276m with two top-hammer and two down-the-hole machines. The average drilling rate per machine at Q2 was 5,910m/month and at Q3 the rate per machine was only 6% lower. So the two quarries were very similar in terms of metres drilled and utilization. It was thus interesting to note that the drilling consumables cost at Q3 ($0.33/m) was 83% higher than at Q2 ($0.18/m). This vast difference came about due to differences in the drilling conditions and high rock tools consumption by the DTH machines at Q3.