Red-hot rivets once flew through the air on every steel building site
Old steel frames were stitched together by four-person gangs. One heated rivets until they glowed cherry red, near 900 degrees Celsius, then tossed them with tongs to a catcher holding an ash-lined bucket. Two more hammered each one home. Cheap bolts eventually put that airborne choreography out of work.
A rivet begins as a smooth metal shaft with a head on one end. Push the plain end through a hole and flatten it, and you get a second head, called the shop head or buck-tail, locking the parts together for good. With a head at each end it can resist being pulled apart, but it is far stronger against shear, the sideways slicing force across the shaft. The idea is ancient: Egyptian spearheads of the Naqada culture, made between 4400 and 3000 BC, carry rivet holes, as do many Bronze Age swords and daggers where hilts were fixed.
On a hot-riveting crew, the catcher dropped each glowing rivet into its hole, a holder braced a heavy bar against the round head, and the riveter pounded the other end into a dome. As the metal cooled it shrank along its length, squeezing the joint tight. Before pneumatic hammers, as on the Titanic, the hammer man was simply called the basher. Two unskilled workers can fit high-strength bolts, however, and the labour cost of skilled crews meant bolts largely took over; the main American steel construction code, in its 14th edition, no longer covers installing structural rivets.
Aircraft still rely on them. A modern airframe holds hundreds of thousands of solid rivets, many of aluminium alloy. Some alloys harden as they age, so they are annealed and then stored below freezing to slow the process, earning them the name ice box rivets.
Solid rivets need someone on both sides of the joint. The fix came from Hamilton Neil Wylie, a Royal Navy reservist who patented a way of closing tubular rivets in 1916 and, working at Armstrong-Whitworth, added a pull-through mandrel in 1927. A tool drags the mandrel through, swelling the far end until it snaps off. The result, later sold as the POP rivet, can be set blind from one side.
Source: Rivet
