There are many types of metal cutting tools used by skilled mechanics of all ratings. As you become better acquainted with your rating, you will probably discover many tools that you use for cutting metal that is not described in this text. In this text, only the basic hand metal cutting tools will be considered.
Snips and shears are used for cutting sheet metal and steel of various thicknesses and shapes. Normally, the heavier or thicker materials are cut by shears.
One of the handiest tools for cutting light (up to 1/16 inch thick) sheet metal is the hand snip (tip snips). The STRAIGHT HAND SNIPS shown in fig. 1-20 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 a 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. want to know more than seeing the link.
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 backward when a cut is being made. Although this feature does make the actual cutting easier, it mars the edges of the metal slightly. 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.
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, HAWKSBILL SNIPS, TROJAN SNIPS, and AVIATION SNIPS.
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 snip, as shown in figure 1-21, or some other narrow – bladed snips, make a spiral cut from the starting hole out toward the scribed circle and continue cutting until the scrap falls away.
To cut a disk in the lighter gauges of sheet metal, use combination snips or a straight blade snips as shown in figure 1-22. First, cut away any surplus material outside of the scribed circle leaving only a narrow piece to be removed by the final cut. Make the final cut just outside of 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 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.
Learn to use snips property. They should always be oiled and adjusted to permit ease of cutting and to produce a surface that is free from burrs. If the blades bind, or if they are too far apart, the snips should be adjusted.
Never use snips as screwdrivers, hammers or pry bars. They break easily.
Do not attempt to cut heavier materials than the snips are designed for. Never use tin snips to cut hardened steel wire or other similar objects. Such use will dent or nick the cutting edges of the blades.
Never toss snips in a toolbox where the cutting edges can come into contact with other tools. This dulls the cutting edges and may even break the blades.
When snips are not in use, hang them on hooks or lay them on an uncrowded shelf or bench.
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