Filing Metal Round.—It is sometimes necessary to file a piece of metal round. This is a hard job, particularly where it is impossible to scribe the end of the piece. Suppose it is necessary to file up a bearing surface, or surfaces, intermediate the ends of a square bar.
You have in that case four sides to start from,[p. 55] the opposite sides being parallel with each other, so that you will have two dimensions, and four equal sides, as shown in [Fig. 50].
The first step will be to file off accurately the four corners 1, 2, 3, 4, so as to form eight equal sides or faces, as shown in [Fig. 51]. If you will now proceed to file down carefully the eight corners, so as to make sixteen sides, as in [Fig. 52], the fourth set of corners filed down will make the filed part look like the illustration [Fig. 53] with thirty-two faces.
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| Fig. 52. | Fig. 53. |
| Making a Bar Round[ToList] | |
This may be further filed down into sixty-four faces, and a few cuts of the finishing file will take off the little ridges which still remain. By using emery cloth, and wrapping it around the bearing portion, and changing it continually, while drawing[p. 56] it back and forth, will enable you to make a bearing which, by care, will caliper up in good shape.
Kinds of Files.—Each file has five distinct properties; namely: the length, the contour, the form in cross section, the kind of teeth, and the fineness of the teeth.
There are nine well-defined shapes for files. These may be enumerated as follows:
No. 1. The cotter file. The small kind is called a verge or pivot file.