Blind Rivet

Record the problem: how do you set a rivet when you can only reach one side? Sketch a closed wing box to see why it matters.

Measure the rivet body diameter and the length of the unset tube with the caliper. Record both. Note the mandrel protruding from the head.

The hole should be a close clearance on the body — typically 0.1 mm over. Write down the drill size your measured rivet needs.

Clamp two aluminium sheet coupons together and drill through both at once, so the holes cannot misalign.

Insert the rivet, squeeze the gun until the mandrel breaks with a distinct snap. That snap is the designed break point doing its job.

Measure the head height now. Compare with step 2: the tube has shortened, and that lost length has become the bulb on the blind side.

Cut through a set rivet with a file or cut-off wheel and look at the section. The formed bulb on the far side is the entire mechanism.

Set an identical rivet through a single sheet only. It is loose — too little material for its grip range, so the bulb forms in air.

Make three identical two-sheet joints, one rivet each. Label them with the marker.

Clamp each specimen and pull with the force meter until it fails. Record the peak force for all three and average them.

Blind rivets fail two ways: the rivet shears, or it pulls through the sheet, tearing a hole. Record which you got — thin sheet gives the second.

Note the trade: a rivet leaves a hole and needs no power at all; a spot weld leaves no hole and needs both sides plus a machine.

The mandrel is fired, not dropped. When it snaps it can leave the gun with real force, and the stub is a hardened steel splinter. Safety glasses are worn for every setting operation, including the first one you think is too small to matter.

Drilling aluminium throws sharp swarf in fine curls that embed in skin, and the drilled coupons carry a burr on the back face that cuts like a blade. Deburr before handling, and never brush swarf away by hand.

Collect the spent mandrels. A dropped mandrel in an assembly is called foreign object debris, and in aviation it is treated as seriously as a bad weld — a loose steel pin inside a control surface can jam it. Modern guns catch them in a bottle for exactly this reason.

Hamilton Neil Wylie, British patent, 1916-1917, “an improved means of closing tubular rivets”. Sources give both 1916 and 1917, and none consulted supplies a patent number. That gap is reported rather than filled — a fabricated number would look more authoritative and be worth less than nothing.

Aircraft made it necessary. Wylie worked for Armstrong-Whitworth Aircraft in the 1920s, and Armstrong-Whitworth brought in the George Tucker Eyelet Company of Birmingham to develop the design further. Their joint refinement produced the version whose mandrel head pops off after setting — the sound that named the product. “POP” is a trade mark, now owned through Stanley Black & Decker; the generic term is blind rivet, and using the trade mark for the category is the same error as calling every vacuum flask a Thermos.

Carl Cherry, and the second wave. In 1936 Cherry, an MIT-trained engineer in California, was brought a production problem by his stepson, a riveter at Douglas Aircraft. His redesign was filed in 1937 and issued in 1939, and Cherry rivets became a standard of American aviation. The pattern is worth noticing: the concept is British and wartime, the industrialisation is American and inter-war, and the same shape repeats right across the history of joining metal.

Why it still wins. A blind rivet needs no electricity, no gas, no skill certification and no access to the far side, and it works on dissimilar materials that cannot be welded to each other at all — aluminium to steel, metal to plastic, metal to composite. In an age of adhesive bonding and laser welding, a hollow tube and a mandrel remain the cheapest way to clamp two sheets you can only touch from one side.