A down the hole drilling machine comprising: an elongated casing having a top end and a bottom end; a fluid powered piston arranged movably inside the casing; a top working chamber at a top side of the piston; a bottom working chamber at a bottom side of the piston; fluid passages and control elements for controlling feeding and discharging pressurized fluid into and out of the working chambers (21, 22) for generating working cycle of the piston wherein the piston has reciprocating movement in impact direction and return direction; an inlet port at the top end for feeding the pressurized fluid; a drill bit connectable to the bottom end portion of the casing and provided with an impact surface facing towards the piston for receiving impacts of the piston; and wherein the piston comprises a longitudinal central opening passing axially through the piston, whereby the piston has an elongated sleeve-like configuration comprising an outer surface and an inner surface; the sleeve-like piston has a solid outer shell, whereby the piston is without any transverse through openings extending between the outer surface and the inner surface; and wherein at least the fluid passages for feeding the pressurized fluid into both working chambers (21, 22) are located inside the central opening of the piston; characterized in that: inside the central opening of the piston is a feed tube comprising an outer feed tube and an inner feed tube arranged inside the outer feed tube; and the inner feed tube extends to the drill bit and a bottom end of the inner tube is located inside a central opening of the drill bit. an elongated casing having a top end and a bottom end; a fluid powered piston arranged movably inside the casing; a top working chamber at a top side of the piston; a bottom working chamber at a bottom side of the piston; fluid passages and control elements for controlling feeding and discharging pressurized fluid into and out of the working chambers (21, 22) for generating working cycle of the piston wherein the piston has reciprocating movement in impact direction and return direction; an inlet port at the top end for feeding the pressurized fluid; a drill bit connectable to the bottom end portion of the casing and provided with an impact surface facing towards the piston for receiving impacts of the piston; and wherein the piston comprises a longitudinal central opening passing axially through the piston, whereby the piston has an elongated sleeve-like configuration comprising an outer surface and an inner surface; the sleeve-like piston has a solid outer shell, whereby the piston is without any transverse through openings extending between the outer surface and the inner surface; and wherein at least the fluid passages for feeding the pressurized fluid into both working chambers (21, 22) are located inside the central opening of the piston; characterized in that: inside the central opening of the piston is a feed tube comprising an outer feed tube and an inner feed tube arranged inside the outer feed tube; and the inner feed tube extends to the drill bit and a bottom end of the inner tube is located inside a central opening of the drill bit. inside the central opening of the piston is a feed tube comprising an outer feed tube and an inner feed tube arranged inside the outer feed tube; and the inner feed tube extends to the drill bit and a bottom end of the inner tube is located inside a central opening of the drill bit.