Permanent and temporary joints
- Permanent joints can't be taken apart without damage: welding, brazing, soldering, riveting and adhesives.
- Temporary (non-permanent) joints can be taken apart: nuts and bolts, machine screws and set screws.
Thermal joining
- Welding melts the edges of the parent metals so they fuse, usually with a filler rod. It is very strong. Types include MIG (a wire electrode fed through a gun with shielding gas), TIG (a tungsten electrode, for precise work) and oxy-acetylene gas welding.
- Brazing uses a brass filler that melts at a lower temperature; the parent metals don't melt. It is weaker than welding.
- Soldering uses a tin alloy filler at an even lower temperature. It is used for electronics and plumbing.
Mechanical fastenings and adhesives
- Rivets are permanent mechanical fasteners. Pop rivets can be fitted from one side, useful for hollow sections.
- Nuts, bolts and washers make strong temporary joints. Locking nuts and spring washers stop them loosening from vibration.
- Adhesives such as epoxy resin can join different materials and spread the load over a large area, but may need time to cure and careful surface preparation.
Welding safety
- Wear a welding mask with a tinted screen (to protect from UV light and sparks), leather gloves and an apron, and work in a ventilated area.
Key terms
- Permanent joint
- A joint that can't be taken apart without damage.
- Temporary joint
- A joint that can be taken apart, such as nuts and bolts.
- Welding
- Melting the parent metals so they fuse together.
- Brazing
- Joining metals with a brass filler, without melting the parent metals.
- Soldering
- Joining with a low-melting tin alloy, often for electronics.
- Rivet
- A permanent mechanical fastener.
- Parent metal
- The metal being joined.