Grades 6–8 · Machines
How can a metal pin hold sheets together without a screw thread?
Rows of small metal heads on an aircraft or old bridge may belong to rivets. A solid rivet starts as a pin with a manufactured head at one end. Its shank passes through aligned holes in the pieces being joined.
The projecting tail is squeezed or hammered while the first head is supported. The tail permanently changes shape, becoming shorter and wider. This forms a second head that is too broad to pass back through the hole.
Compare the straight tail before forming with the wide head afterward. Opposing horizontal arrows show a possible sliding load.
The two heads keep the sheets captured. When the sheets try to slide past each other, their hole edges bear against the shank, which resists being sheared across. Friction between tightly clamped sheets can also help transfer load; the balance depends on the joint.
Rivets are not tiny welds, and a solid rivet does not unscrew. Removing one commonly requires machining away part of it. Hole size, spacing, material and the way the second head forms all affect strength.
The connection turns a controlled, permanent shape change into a lasting restraint. A pin that could once slide through the holes becomes a fastener because one end can no longer fit through them.
About this explanation
This is a schematic solid-rivet joint, not a blind rivet or an installation specification; load sharing depends on design.
Starting knowledge: Know that metal can be permanently shaped and that forces can try to slide joined parts apart.
Sources
- Federal Aviation Administration — Airframe and Powerplant Mechanics General Handbook: rivets