factory head
The head formed when a rivet is manufactured, as opposed to the shank (or bucktail), the end of which will be upset to form the field head, after it is inserted through the materials to be connected.
factory head: the rivet's made end, before it goes to work
A factory head is the end of a rivet that is formed during manufacture, before the fastener leaves the supplier. It is a solid, finished head that remains intact during installation. The opposite end, called the shank or bucktail, is the part that gets inserted through the holes in the materials being joined. After the shank passes through, it is upset (deformed under force) to create a second head, known as the field head or shop head, which locks the joint together.
The factory head must be robust enough to withstand the forces applied during the upsetting process without deforming or fracturing. Common shapes include countersunk, universal, flat, and button heads. The head diameter is typically 1.5 to 2 times the shank diameter, and this ratio affects how cleanly the rivet seats in a countersunk hole or bears against a surface. The transition between head and shank is usually filleted to reduce stress concentration.
Manufacturing and material specifications
Factory heads are formed by heading machines that strike heated or cold rivet blanks. The process must produce heads with consistent dimensions, because undersize heads will pull through holes or fail to bear properly, while oversize heads cannot be driven flush. Rivets are made from mild steel, aluminum alloys, copper, monel, and stainless steel depending on the joint requirements and environment. Material choice affects both the heading process and the strength of the finished joint.
The factory head sits against the material surface and distributes load over an area. If the head is too small or poorly formed, it will sink into soft material or create a stress riser. In structural work such as aircraft assembly or bridge fabrication, the factory head's geometry is inspected to ensure repeatability. Rivets with damaged or misshapen factory heads are scrapped because a poor factory head cannot be corrected during installation.
The term distinguishes between what the manufacturer controls and what the worker controls. The factory head is fixed and non-negotiable; the field head is created by the rivet gun operator and must be formed correctly to develop full joint strength. Understanding this separation is essential for quality control, because defects in the factory head are introduced before the rivet ever leaves the supplier, while defects in the field head reflect installation technique.