DTH (Down the hole) drilling is a rotary percussive drilling method. Hammer which is used for generating strong impacts is attached to the bottom of the drill string and a drill bit is attached to the lower end of the DTH hammer. The movement of the piston in the DTH hammer is caused by high pressure compressed air. The shock waves that travel to the bit are passed on to the rock mass through the cutting edges or carbide buttons on the bit. As a result, cracks are formed in the rock mass which results in formation of rock chips. Cuttings are removed from the hole by the air circulated from bottom to top to flush the hole.