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barrel grinding machine. This machine is in effect a lathe in which the barrel is revolved slowly between centers, but instead of a cutting tool a grinding wheel running at high speed is brought against the barrel's surface; and this wheel, as it travels the length of the barrel, is guided so as to follow its taper formation exactly. Thus the barrel is brought to its finish dimensions, and comes from the grinding machine with a very smooth, bright surface. Nevertheless, the "grain" of the grinding is around the barrel, whereas it should run lengthwise, and must be polished oif. On a barrel that has been ground very little striking is needed—sometimes none at all.

Fig. 120

The principal tool needed is a large, wide, and very fine cut file. The best for the purpose is an American Swiss, a Nicholson, or a Disston "pillar file" as described in Chapter 3. This should be at least ten inches long, and at least an inch in width—the wider the better. A wide file follows the straight surface of the barrel, while a narrow one tends to cut unevenly, giving it an 'ocean-wave'' effect as you look down the sights.

These pillar files are available in much finer cut than ordinary machinists' files. Ordinarily the 00 cut is about right for striking, but if a particularly good job is wanted, the barrel may be struck again with a file having a 0000 cut.

Using heavily padded vise-blocks to prevent damage, hold the action in the vise with the barrel's entire length available for the work. Keep a piece of chalk handy, and chalk the cutting side of the file all over at frequent intervals. This prevents the particles of steel from the barrel from clogging the file teeth, or "pinning" as it is termed. If this occurs, deep scratches will be gouged in the barrel which will be difficult to strike out. The file card, or brush

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