Tin snips are one of the easiest and most accessible ways for beginning metalworkers to cut shapes in metal. Cut shapes in aluminium sheeting to allow pipes to pass through it or to fit the sheeting around fixtures. Cut decorative shapes in aluminium sheeting and place it in front of copper sheeting to highlight the cutouts. Buy tin snips at a home improvement or hardware store. There are different types of tin snips with blades that are meant to make curved or straight and short or long cuts. Make sure to use the right blades for the cuts you intend to make.
Draw the shape on the aluminium sheet with a felt-tipped marker on the "wrong" side of the aluminium, the side that will not show.
Put on heavy-duty work gloves to protect your hands from the sharp edges of the cuts. Wear goggles to protect yourself from sharp metal shards that could fly up into your face.
Punch a starter slot in the middle of the traced shape by placing the head of a screwdriver against the sheet metal and tapping it with a hammer until it breaks through the metal. Use a regular screwdriver, not a Phillips screwdriver.
Choose the right tin snips to use. Use snips with long straight blades if you are making long cuts, and snips with short blades for short cuts. Use snips with a curved blade for curved cuts.
Place the bottom blade in the starting hole and cut toward the outline of your shape. Cut along the outline when you get to it. Pull up on the bottom blade rather than down on the top blade like you do for scissors. This will prevent the metal from bending and will create smoother lines. Do not completely close the jaws of the tin snips as this could cause the aluminium to tear perpendicular to the cut.
Pull the excess aluminium away from the tin snips with your other hand as you cut. This will prevent it from hitting the snip's handle.
Always purchase high quality tin snips that are very sharp and that have spring action. This will make it easier to make cuts. If you are left-handed purchase special tin snips to accommodate you. If you are cutting a lot of shapes in aluminium sheeting, consider purchasing a sheet metal nibbler. Nibblers cut away at the metal without bending it, and you can use the same nibbler for making curved or straight cuts.
Be careful not to cut yourself on the sharp metal edges. If you are making something for home use, make sure that the cut edges are smoothed before you put in within the reach of children. Use a metal file or sandpaper made for working with metal, such as aluminum oxide sandpaper, to smooth the edges.