Clinching, riveting and welding thin sheet
Clinching
Section titled “Clinching”A tool-formed joint with no fastener: the tool presses the two sheets into each other and the resulting interlock holds them together.
Advantage
Section titled “Advantage”Fast, no fastener cost, no corrosion question around a screw, and easy to automate in factory conditions.
Its capacity in one direction is lower than a screw’s, and the form is tied to the tool. It is used in factory, panelised production, not on site.
Blind rivet
Section titled “Blind rivet”A fastener that can be installed with access from one side only. Useful where the far side cannot be reached — at a closed section, or connecting to an existing structure.
The limits on its capacity are similar to a screw’s: the behaviour of the sheet decides.
Welding
Section titled “Welding”Technically possible, but problematic in thin sheet for several reasons:
- burn-through: thin material burns through easily,
- destruction of the coating: the heat vaporises the zinc, creating a corrosion weak point — and raising health questions as well,
- quality control: the quality of a weld in thin sheet is hard to check,
- site conditions: the quality of site welding varies.
Hence industry practice is the screwed connection. Welding comes up where a connection is made to a thicker member — hot-rolled steelwork, say — and there too on the thicker side. Hot-rolled steel and mixed structures.
Adhesive bonding
Section titled “Adhesive bonding”It appears in a supporting role — fixing boards, for example — but not as a structural connection in building construction, because ageing and behaviour in fire are hard to handle.
How to choose
Section titled “How to choose”- Where it is made: factory or site.
- Access: one side or both.
- Capacity and deformation: how much force, how much movement is allowed.
- Checkability: whether it can be seen afterwards that it was done properly.
- Demountability: if the member may have to come out later, the screw wins.
The point
Section titled “The point”The screwed connection is not tradition but a choice: checkable, demountable, and it does not damage the corrosion protection. The other methods have their place, but in factory conditions.