Abstract: An improved air replenishing and idling system for a reciprocating hammer type tool having an outer housing and reciprocal drive mechanism, comprising an elongated barrel mounted within that housing. The barrel includes an axially disposed, air passageway. Slideably positioned within the barrel is a piston member which includes a closed end portion and a hollow, tubular forward portion having first and second air passageways. The piston is reciprocally moved within the barrel by the drive mechanism. Slideably positioned within the hollow tubular portion of the piston is an impact ram. In the operational mode, the ram, tubular portion of the piston member, and barrel cooperate to seal or expose the first and second air passageways and provide a communicative path to the "outside" air through the barrel air passageway whereby the ram is urged axially towards and away from the tool bit through the pressure differentials created.