of the half round file, known as a wood rasp; the other being thinner, and with a much more flat curve on the one side, known as a cabinet rasp. The latter is best for gun work. In using it, hold the handle in right hand, and the point in left hand. As you push forward alsu move the rasp sideways, making a diagonal stroke, the rasp being turned at an angle of about 30 degrees with the work. This gives a very even cut over two or three inches of surface, whereas pushing the tool straight in line would merely cut a groove its own width. Always use the rounded side for the first roughing curs,
using the flat side when the stock has been reduced to almost its final shape.
The cabinet file is similar in shape to the rasp, and is used in the same manner. Having finer teeth it makes a smoother cut. This is the tool to use for the final truing up of the surface of a stock, before the first coarse sanding. Some stockers follow the cabinet file with another cut using a common mill file—but this cuts very slowly on wood, and the file teeth also clog badly. Very light finishing strokes with the cabinet file will leave the wood in very good condition for rhc sandpaper.
FILES AND FILING. Some day I hope to know enough—provided I live long enough—to write a book on this subject alone. It ¡6 one of the fundamental mechanical oubjecte, and one which might easily require the space of this entire volume—and still not tell half the story. The file is the basis of practically all cutting operations in the machine shop; the milling cutters, profile cutters, etc., are really files; a broach is a file; the cutter on a rifling head is a single tooth filr—and is the cutter on the planer or shaper. Even the lathe operations are based on the fundamental principles of filing— the tool being the file, which is held stationary, while the work is revolved against it.
Given the right files, a first class mechanic can make by hand almost any part ordinarily made on machines. Slower—yes; but it can be done. Such a man kqows and understands that the file is an important cutting tool, designed for shaping and forming; while the layman usually thinks of it as something to scratch or smooth the surface. He seldom considers that there is a right file for the job at band, and knows only that there are flat files, "three cornered" files, and rotrails. He usually goes into the store, and says "Gimme a small file;—Oh, about six inches, I reckon; yeah, that'n'll be all right." Then he takes it and skims over the surface of whatever it is he is spoiling, often making no impression to speak of, and at other times misshaping the article badly.
If I included too great a number of different files in ray recommendations in Chapter 3, it was because I realize the need for various shapes and sizes, and know how the possession of the right file for the job will speed up work and save cost.
One of the first lessons to be learned in the matter of filing is to take all the short cuts possible—otherwise the job becomes so tedious that one tires of it and gives it up in disgust. I have seen a man scouring away for three hours on a bar of steel with a fine mill file, trying to take off nearly a quarter inch of metal. It never occurred to him, for some strange reason, to saw the strip off close to the line with the hacksaw, and finish with a file.
Before going into these short cuts however, the amateur mechanic should first know how to use a file; to make his strokes in a straight line, without rocking the file, resulting in a perfectly flat surface instead of a rounding one. Once this is learned any man can acquire proficiency with the file; and until and unless it is learned, his work will be of the crudest, most amateurish type.
Whatever it is you are filing, it must be held very firmly in the vise. When a part wobbles about this way and that, you cannot file it correctly. Use leather, brass, sheet lead or whatever is necessary, to hold it, but set it up solid. Lay the file evenly on the flat surface of the work; hold the handle in the right hand, the point in the left, and swing the arms forward in a full body movement, keeping the file constantly in the same plane. Despite your best efforts the file will rock, and the surface will be rounded. No matter how flat you think it is, just hold it up to the light with a small square or straightedge touching the surface, and the curve will be plain. Only practice, with constant thought to the direction of the stroke and the movement of the hands, will correct this fault.
I am a firm believer in coarse, fast cutting files. I never could see anything gained by prolonging the job with a slow tool. If there is 1/32 inch or more of metal to be removed, I will use a medium cut bastard file until I almost reach the line, then go ahead with a medium fine single cut or mill file, and finish with a fine cut Swiss. Getting rid of surplus metal quickly relieves much of the monotony —and believe me, even the coarsest file doesn't reduce dimensions nearly so fast as it seems. Measurements with a micrometer after a few cuts will show how fast the work really progresses—and it is
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