This glossary defines the bucking-bar and riveting terms used across the site.

Bucking bar

A dense metal bar held against the tail of a solid rivet so the shop head forms cleanly while the rivet is driven.

Shop head

The upset head formed on the tail of a solid rivet when it is driven against a bucking bar.

Manufactured head

The original factory-formed head of a solid rivet, on the rivet-gun side of the joint.

Bucktail

The protruding tail of a solid rivet that upsets into the shop head under the bucking bar.

Rivet gun

The pneumatic tool that hammers the manufactured head while the bucking bar backs the tail.

Solid rivet

A one-piece rivet set by driving the manufactured head while a bucking bar reacts the tail.

Tungsten heavy alloy

A high-density material that is mostly tungsten with a small nickel-iron or nickel-copper binder. It is what gives a bucking bar its mass in a compact size. Read more about tungsten heavy alloy.

Density

Mass per unit volume. Tungsten alloy is about 2.5 times as dense as steel, which is why a smaller bar carries the same bucking mass. See tungsten material properties.

Weight class

A grouping of bars by weight (light, medium, heavy, extra-heavy) used to match a bar to rivet size.

Access type

How the rivet location is reached (open, tight, edges and flanges, deep reach), which drives the bar shape.

Reach bar

A long, slim bar that carries bucking mass to a rivet set well in from an edge.

Low-profile bar

A thin bar, about 0.5 in or less, for shallow and confined access.

Back riveting

A method where the bucking bar (often a flat-faced bar) backs the manufactured head while a flush set on the gun drives the shop head from the skin side, used for a smooth exterior.

Flush rivet

A countersunk or dimpled solid rivet whose head sits flush with the skin, common on exterior aerodynamic surfaces.

Dimpling

Forming a conical depression in thin sheet so a flush rivet head seats flush, used where the sheet is too thin to countersink.

Work hardening

The hardening of metal from repeated working. Over-driving a rivet or excessive hammering work-hardens the joint; a properly massed bucking bar sets the head in fewer, cleaner blows.

Edge distance

The distance from the center of a rivet to the edge of the sheet, a layout rule that affects joint strength and how a bar must be positioned.

Tipping

When a bucking bar is not held square to the rivet tail and the shop head forms lopsided. Matching bar shape to the access helps keep the bar flat and avoid tipping.