Chapter 11
Hand Tools & Measuring Devices
steady with a speed not more than 40 to 50 strokes per minute.
- After completing the cut, remove chips from the blade, loosen tension on the blade, and return the hacksaw to its proper place.
Chisels
A chisel is a hard steel cutting tool that can be used for cutting and chipping any metal softer than the chisel itself. It can be used in restricted areas and for such work as shearing rivets, or splitting seized or damaged nuts from bolts. [Figure 11-15]
The size of a flat cold chisel is determined by the width of the cutting edge. Lengths vary, but chisels are seldom under 5 inches or over 8 inches long.
Chisels are usually made of eight-sided tool steel bar stock, carefully hardened and tempered. Since the cutting edge is slightly convex, the center portion receives the greatest shock when cutting, and the weaker corners are protected. The cutting angle should be 60° to 70° for general use, such as for cutting wire, strap iron, or small bars and rods. When using a chisel, hold it firmly in one hand. With the other hand, strike the chisel head squarely with a ball peen hammer.
When cutting square corners or slots, a special cold chisel called a cape chisel should be used. It is like a flat chisel except the cutting edge is very narrow. It has the same cutting angle and is held and used in the same manner as any other chisel.
Rounded or semicircular grooves and corners that have fillets should be cut with a roundnose chisel. This chisel is also used to re-center a drill that has moved away from its intended center.
The diamond point chisel is tapered square at the cutting end, and then ground at an angle to provide the sharp diamond point. It is used for cutting B-grooves and inside sharp angles.
Files
Most files are made of high-grade tool steels that are hardened and tempered. Files are manufactured in a variety of shapes and sizes. They are known either by the cross section, the general shape, or by their particular use. The cuts of files must be considered when selecting them for various types of work and materials.
Files are used to square ends, file rounded corners, remove burrs and slivers from metal, straighten uneven edges, smooth rough edges, and file holes and slots. Files have three distinguishing features:
- Their length, measured exclusive of the tang [Figure 11-16];
- Their kind or name, such as a hand file shown in Figure 11-16, that has reference to the relative coarseness of the teeth; and
- Their cut, such as a single- or double-cut file.
Files are usually made in two types of cuts: single cut and double cut. The single cut file has a single row of teeth extending across the face at an angle of 65° to 85° with the length of the file. The size of the cuts depends on the coarseness of the file. The double cut file has two rows of teeth that cross each other. For general work, the angle of the first row is 40° to 45°. The first row is generally referred to as “overcut,” and the second row as “upcut;” the upcut is somewhat finer than and not as deep as the overcut.
Care and Use
Files and rasps are catalogued in three ways: