Abstract: A drill bit for drilling a subterranean bore hole which includes a housing having a cap plate adapted for connection to a drill pipe and a base block axially aligned with and spaced from the cap plate by guide members. A plurality of elongated drill rod impact members are carried by a drill rod holder plate disposed between the cap plate and base block for movement longitudinally of the housing. The free ends of the drill rods extend through guide bores in the base block to define exposed working ends for chipping and crushing the formation upon rotation of the drill bit and the introduction of drilling fluid into the housing in a manner to effect a hammer-like action of the drill rods and progressively move them longitudinally outwardly from the base block as they undergo wear.