Understanding Airplane Rivets

Airplane Rivets

Airplane Rivets

Universally taught at all aircraft mechanic schoolsairplane rivets are a time-honored method of attaching two metal surfaces together, with a lasting attachment. Rivets are superior to welds.

In many non-aviation situations, a “pop rivet” can be attached to fasten two surfaces, using a pop rivet gun. The general idea is to use a rivet with a “shank” and a “mandrel”. The pop rivet gun pulls on the top of the mandrel, exposing the shank.  As the shank expands, continued pulling on the mandrel clamps the two metal surfaces together. Continued force from the pop rivet gun then snaps off the mandrel head, at a pre-fashioned break point. When the rivet head comes off, it makes a “popping” noise.

The following video shows conceptually what happens as one attaches a pop rivet. Note especially what happens to the mandrel and shank as the rivet is formed.

However, unlike the pop rivets, most aircraft use a solid rivet.  These solid rivets are unthreaded pins of aluminum alloy, with a head on one end. Normally, a pneumatic rivet gun and a bucking bar are used as the two tools needed to attach a rivet. Rivets come in various sizes,and have either a “Universal Head”  or a “countersunk” head. By convention, rivet sizes increment in steps of 1/32″. Rivet diameters range from 3/32″ to 1/4″.  Additionally, rivet lengths go up in steps of 1/16″.

A properly installed rivet will have a diameter about 3 times the thickness of the thickest airframe sheet used.  A good rule of thumb is to assure the rivet length protruding from the far side of the hole is approximately 1.5 times the diameter of the hole in the metal.

Essential tools in installing a rivet are a pneumatic rivet gun, and a bucking bar. To install a rivet, first drill and de-burr holes on both sides, in both metal skins. Then install a bucking bar in a vise. With the bucking bar on one side of the two sheets, and a pneumatic rivet gun on the other side, set the rivet gun pressure. Then, have the gun and rivet held at a 90 degree angle to the metal surface. Apply a gentle, persistent  pressure to the pneumatic gun until the rivet forms.

If a vise can’t be used, typically for work directly on an aircraft, two aircraft mechanics must work together. One holds the bucking bar in place, while the other mechanic operates the pneumatic rivet gun on the other side of the two surfaces.

by Steve Adams

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