Pneumatic tool with as-cast air signal passage

A fastener driving device includes a housing containing a chamber for storing compressed air a cylinder structure disposed within the housing, a piston movably disposed within the cylinder, a driver connected to the piston, a main valve cooperable with the cylinder structure and movable between an open position and a closed position. The main valve in its open position allows air to move the piston through a drive stroke. The fastener driving device also includes a trigger valve operable between first and second positions. The trigger valve in its first position communicates air pressure from the chamber to the main valve through a signal passageway so as to retain the main valve in a closed position. The trigger valve in its second position allows the air to be exhausted to atmosphere through the signal passageway to permit the main valve to open. The cylinder and the signal passageway comprise an integrally molded structure.