Rotary drilling is mostly used to drill big holes in large quarries, open pit mines, petroleum extraction, and other fields. Fig. 7.6 shows a diagram of a rotary drilling system. There are two groups of big rotary drilling: (1) rotary crushing by high-point loading to the rock from three cones, as shown in Fig. 7.7 a, and (2) rotary cutting by shear force from drag bits, as shown in Fig. 7.7 b.