Bucking

The process in which a shop head is formed on a solid aircraft rivet. The rivet is inserted into holes drilled through the metal sheets being joined. The manufactured head of the rivet is hammered with a pneumatic hammer through a rivet set that fits the shape of the head. A hardened-steel bucking bar is held against the shank of the rivet, and the hammering causes the end of the shank to expand and become shorter, forming the shop head that clamps the metal pieces together.