Non-ferrous metals; working with wire and sheet

A long metal rod of cross-section diameter up to 8 mm is called wire. Wire kept long or coming off a coil is crooked, so after cutting it is straightened: soft wire by light blows on a plate, by pulling with pliers, or by drawing it through two pieces of wood with a smooth rod. Aluminium and copper wire are best straightened with a wooden mallet because a steel hammer leaves marks. Wire up to 3 mm in diameter is cut with pliers or nippers; thicker wire with a chisel on an anvil or with a hacksaw. In bending, flat-jaw pliers make angles and round-jaw pliers make curves; rings and springs are made by winding wire onto a cylindrical mandrel fixed in the vice. A dented sheet is straightened on a steel plate with light blows in a spiral around the bulge, never on the bulge itself. Marking is done with a scriber, rule, compasses and try square; on tinned or galvanised sheet a pencil is used because a scriber breaks the protective layer. When cutting, the gap between shear blades must be very small (0.1–0.2 mm). Wear goggles and gloves for metalwork, hold the wire piece so the ends do not fly, and smooth sharp ends and edges with a file. Sheet metal and shears are used under the teacher’s supervision.