Hand hacksaw
The pistol grip hacksaw (Fig. 7-5) consists of three main parts: frame, blade, and adjusting wing nut.
The frame on hacksaws of this type can be adjusted to hold saw blades that are 8, 10, or 12 inches long. When inserting a blade always make sure that the teeth are pointing away from the handle, and draw the blade tight with the wing nut.
Hacksaw Blades. Hacksaw blades are made of high-speed, molybdenum, or tungsten alloy steel that has been hardened and tempered. The saw blades generally used are from 8" to 12" long, y2" wide, and .025 thick. There is a hole at each end for mounting them on the hacksaw frame. The distance between each tooth on a blade is called the pitch. (1/18 pitch represents 18 teeth per inch). The commonest blades have 14, 18, 24, or 32 teeth per inch. An 18-tooth blade (18 teeth per inch) is recommended for general use in hand hacksaws. It is important to use the right saw for the work being cut. Select a blade as coarse as possible but one which will always have two teeth in contact with the work. Such a blade will provide plenty of chip clearance and cut through the work quickly.
Fig. 7-5. Parts of a pistol-grip adjustable hacksaw
To Use the Hacksaw
1. Hold the hacksaw as illustrated in Fig. 7-6.
2. Hold the work securely and fairly close to the vise to prevent its springing or coming loose.
3. Always start cutting on the forward stroke.
4. Apply pressure on the forward stroke and release pressure on the return stroke.
5. After a cut is started, use approximately 50 strokes per minute.
6. When nearing the end of the cut, slow down so that you can control the saw when breaking through the material.
7. For easier starting, it is wise to first make a small nick with the edge of a file.
8. A fairly thin piece of metal may be sawn easily by clamping it between two pieces of
wood (Fig. 7-6). Use the finest blade and saw through the wood and metal.
When entering a new saw into an old cut, do not apply pressure until the saw is at the bottom of the cut. The'set of teeth on a new blade is slightly wider than the cut made by the old blade. If possible, it is better to turn the work piece and start the new blade in another place.
Fig. 7-6. Sawing a thin piece of metal