Abstract: A pneumatically operated nailing machine having a reciprocatable blade for driving nails when advanced, and a reciprocatable differential piston unit connected to the blade. The reciprocatable differential piston unit has an upper, small diameter piston and a lower, large diameter piston interconnected by a piston rod. The upper, small diameter piston has valve means for venting any air under pressure therebelow to atmosphere when the blade is advanced by the reciprocatable differential piston. Nail guide and positioning means are provided for the machine for maintaining each nail of a nailing strip in proper alignment with the blade and a workpiece when the blade is advanced. Nail feeder means is provided for the machine for maintaining the nails of a nailing strip in proper alignment as they are sequentially advanced into the nail guide and positioning means.