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Joining metals

Rivet heads: snap (round), countersunk, flat and pop rivets (used where only one side can be reached). A rivet set and snap shape the head.

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Temporary and permanent joints

  • Temporary: nuts and bolts, screws, machine screws – can be taken apart.
  • Permanent: rivets, soldering, brazing, welding, adhesives.

Riveting

Rivet heads: snap (round), countersunk, flat and pop rivets (used where only one side can be reached). A rivet set and snap shape the head.

Soft soldering

Uses solder with a flux (to clean the joint and stop oxidation) and a soldering iron; used for electrical work and tinplate. Low strength.

Brazing (hard soldering)

Uses brass spelter and borax flux at a higher temperature (gas torch); stronger than soft soldering.

Welding

Melts the parent metals together, usually with a filler rod.

  • Arc welding: an electric arc between an electrode and the work; used for steel fabrication (gates, frames).
  • Gas (oxy-acetylene) welding: a hot flame; can also cut steel.

Safety: helmet with filter lens, gloves, ventilation, keep flammables away.

Adhesives

Epoxy resin joins metals to themselves or other materials.

Exam tip: Compare joining methods by strength, temperature needed and whether the joint is permanent.

Check yourself

  1. Give one use of pop rivets.
  2. State the purpose of flux in soldering.
  3. Which joining method is commonly used to make steel gates?
Show answers
  1. Joining where only one side of the work can be reached (e.g. sheet metal boxes, gutters).
  2. To clean the joint, prevent oxidation and help the solder flow.
  3. Arc welding.
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