Abstract: A down hole hammer comprises a top sub and a drill bit support supporting a drill bit separated by a tubular housing to define a piston chamber therebetween. A feed tube is mounted to the top sub and extends concentrically into the piston chamber. A piston is slidably received within the housing and over the feed tube. Fluid porting is provided in the feed tube and the piston to sequentially admit fluid to a first space between the piston and top sub to drive the piston towards the drill bit support and to a second space between the piston and the drill bit support to drive the piston towards the top sub.