CHISELS

kerf. Put an adjustable wrench across this new flat and the one opposite, and again try to remove the frozen nut. Since very little original metal remains on this one side of the nut, the nut will either give or break away entirely and permit its removal. To saw a wide kerf in the head of a cap screw or machine bolt, fit the hand hacksaw frame with two blades side by side, and with teeth lined up in the same direction. With slow, steady strokes, saw the slot approximately one-third the thickness of the head of the cap screw, as shown in figure 1-18. Such a slot will permit subsequent holding or turning with a screwdriver when it is impossible, due to close quarters, to use a wrench. Hacksaw Safety The main danger in using hacksaws is injury to your hand if the blade breaks. The blade will break if too much pressure is applied, when the saw is twisted, when the cutting speed is too fast, or when the blade becomes loose in the frame. Additionally, if the work is not tight in the vise, it will sometimes slip, twisting the blade enough to break it. CHISELS Chisels are tools that can be used for chipping or cutting metal. They are made from a good grade of tool steel and have a hardened cutting edge and beveled head. Chisels are classified according to the shape of their points, and the width of the cutting edge denotes their size. The most common shapes of chisels are the flat (cold chisel), cape, round nose, and diamond point (fig. 1-19). The type of chisel most commonly used is the flat cold chisel, which serves to cut rivets, split nuts, chip castings, and cut thin metal sheets. The cape chisel is used for special jobs like cutting keyways, narrow grooves, and square corners. Round-nose chisels make circular grooves and chip inside corners. Finally, the diamond-point is used for cutting V-grooves and sharp corners. As with other tools, there is a correct technique for using a chisel. Select a chisel that is large enough for the job. Be sure to use a hammer that matches the chisel; that is, the larger the chisel, the heavier the hammer. A heavy chisel will absorb the blows of a light hammer and will do virtually no cutting. When using a chisel for chipping, always wear goggles to protect your eyes. If others are working close by, see that they are protected from flying chips by erecting a screen or shield to contain the chips. Remember that the time to take these precautions is before you start the job. FILES There are a number of different types of files in common use, and each type may range in length from 3 to 18 inches. 1-13 Figure 1-18.—Cutting a wide kerf in the head of a cap screw or bolt. Figure 1-19.—Types of points on metal-cutting chisels.