Doofor DF550S hydraulic rock drill Description Doofor DF550S is a high frequency hydraulic rock drill for general excavations, underground production drilling and pilot hole drilling in quarries. The DF550S is recommended for use with 45mm steels. The rock drill flushing head is separated and the flushing head components are made of plastic material to minimize corrosion. Flushing can be done with air or water. Doofor DF550S is ideal for drilling up to 64mm [2 ½―] (maximum 70mm [2 ¾‖]) holes. The rock drill can be equipped with shank adapters (striker bars) R32, R38, T38 and T45 (recommended).