Riveters from H. Hansen Industries work on the Liberty ship SS John W. Brown
at Colonna's Shipyard, a ship repair facility located in the Port of Norfolk, Virginia
. (December 2014)
A rivet gun, also known as a pneumatic hammer, is a type of tool used to drive rivets. The rivet gun is used on rivet's factory head (the head present before riveting takes place), and a bucking bar is used to support the tail of the rivet. The energy from the hammer in the rivet gun drives the work and the rivet against the bucking bar. As a result, the tail of the rivet is compressed and work-hardened. At the same time the work is tightly drawn together and retained between the rivet head and the flattened tail (now called the shop head, or buck-tail, to distinguish it from the factory head). Nearly all rivet guns are pneumatically powered. Those rivet guns used to drive rivets in structural steel are quite large while those used in aircraft assembly are easily held in one hand. A rivet gun differs from an air hammer in the precision of the driving force.
Rivet guns vary in size and shape and have a variety of handles and grips. Pneumatic rivet guns typically have a regulator which adjusts the amount of air entering the tool. Regulated air entering passes through the throttle valve which is typically controlled by a trigger in the hand grip. When the trigger is squeezed, the throttle valve opens, allowing the pressurized air to flow into the piston. As the piston moves, a port opens allowing the air pressure to escape. The piston strikes against the rivet set. The force on the rivet set pushes the rivet into the work and against the bucking bar. The bucking bar deforms the tail of the rivet. The piston is returned to the original position by a spring or the shifting of a valve allowing air to drive the piston back to the starting position.