Cutting Sheet Metal with Snips

have blades that are straight and cutting edges that are sharpened to an 85-degree angle. Snips like this can be obtained in different sizes, ranging from the small, 6-inch, to the large, 14-inch, snip. Tin snips will also work on slightly heavier gauges of soft metals, such as aluminum alloys. Snips will not remove any metal when a cut is made. There is danger, though, of causing minute metal fractures along the edges of the metal during the shearing process. For this reason, it is better to cut just outside the layout line. This procedure will allow you to dress the cutting edge while keeping the material within required dimensions. Cutting extremely heavy gauge metal always presents the possibility of springing the blades. Once the blades are sprung, hand snips are useless. When cutting heavy material, use the rear portion of the blades. This procedure not only avoids the possibility of springing the blades but also gives you greater cutting leverage. Many snips have small serrations (notches) on the cutting edges of the blades. These serrations tend to prevent the snips from slipping backwards when a cut is being made. Although this feature does make the actual cutting easier, it mars the edges of the metal slightly. You can remove these small cutting marks if you allow proper clearance for dressing the metal to size. There are many other types of hand snips used for special jobs, but the snips discussed here can be used for almost any common type of work. Cutting Sheet Metal with Snips It is hard to cut circles or small arcs with straight snips. There are snips especially designed for circular cutting. They are called CIRCLE SNIPS, HAWKS-BILL SNIPS, TROJAN SNIPS, and AVIA- TION SNIPS (fig. 1-9). To cut large holes in the lighter gauges of sheet metal, start the cut by punching or otherwise making a hole in the center of the area to be cut out. With an aviation snips, or some other narrow-bladed snips, make a spiral cut from the starting hole out toward the scribed circle, as shown in figure 1-10, and continue cutting until the scrap falls away. To cut a disk in the lighter gauges of sheet metal, use a combination snips or a straight-blade snips, as shown in figure 1-11. First, cut away any surplus material outside the scribed circle, leaving only a narrow piece to be removed by the final cut. Make the final cut just outside the layout line. This will permit you to see the scribed line while you are cutting and will cause the scrap to curl up below the blade of the snips, where it will be out of the way while the complete cut is being made. To make straight cuts, place the sheet metal on a bench with the marked guideline over the edge of the bench and hold the sheet down with one hand. With the other hand, hold the snips so that the flat sides of the blades are at right angles to the surface of the work. If the blades are not at right angles to the surface of the work, the edges of the cut will be slightly bent and burred. The bench edge will also act as a guide when you are cutting with the snips. The snips will force the scrap metal down so that it does not interfere with cutting. Any of the hand snips may be used for straight cuts. When notches are too narrow to be cut out with a pair of snips, make the side cuts with the snips and cut the base of the notch with a cold chisel. 1-10 Figure 1-10.—Cutting an inside hole with snips. Figure 1-11.—Cutting a disk out of sheet metal.