Complete with triple air/water swivel,kelly bar,triple drillpipe,heavy centralizer,etc,,the singleheaded large diameter DTH hammer can be used to perform advanced drilling technique which combines DTHrock drilling,cuttings removal with reverse circulation by pump suction,hole wall protection with mud and pres-surized air circulation in a closed loop.It is an effective tool to tackle large diameter hard rock and boulderdrilling problems,Development and design of the tool are described.