Rock drill operations are classified as top hammer drilling (THD), down-the-hole drilling, or rotary drilling. The rock drill in the THD method consists of a percussion drill rig module and a drill bit. The percussion drill rig module consists of a drifter, feed drive, and auto rod changer. In particular, the drifter generates the impact and rotational force for drilling. The purpose of this study was to analyze the hydraulic circuits of the drifter and to develop an analysis tool for analyzing the impact capability. This study also analyzed the capability of the drifter with regard to the penetration rate and varying kinetic energy, which is dependent on rock stiffness, using the developed analysis tool.