by J.M.Drew St. Paul Publishing Company 1918
- HOME -Farm Blacksmithing
In the average farm shop there is usually to be found one, or perhaps two or three files in, generally, a rather advanced stage of wear. With this one, or these two or three files the farmer tries to do all his filing. It he is enough of a mechanic to try to file his own saw, he will have one or two three cornered files. As a rule a corn cob serves as a handle for the farmer's file if any handle is used.
The farm mechanic ought to know that it is more economical of money and time to have at hand an assortment of files suited to different kinds of work, than to attempt to do all kinds of filing with one or two files. This will be better understood after some discussion of the use of files. Files are classified in three ways; first, according to length, second according to shape of cross section, and third according to cut. The length of a file or rasp is always measured exclusive of the tang and is given in inches. Files are made in an almost endless variety of shapes of cross section, but those in most common use are flat files, (having a width of five times the thickness), mill files (with a width of three times the thickness), triangular files, sometimes called "3 square," round or rattail files, and half rounds. The cut of files is designated by the terms, single cut, double cut and rasp cut; and the coarseness or fineness of cut by the terms, rough, coarse, bastard, second cut, smooth and dead smooth. The rough and dead smooth files are very seldom used in ordinary practice.
Coarse and bastard cut files are used for ordinary rough work where the object of filing is to remove quantities of metal rather than to make a smooth finish. Second cut and smooth files are used for finishing work. Single cut files are those which have a single course of chisel marks or cuts, (usually at an angle of 45 degrees) from end to end of the file. Double cut files have two courses of chisel cuts crossing each other forming raised angular teeth, instead of ridges. Rasps or rasp cut files differ from the others in having teeth standing out separate from each other, which are made by a diamond-pointed, instead of flat chisel.
THE USE OF FILES
If the amateur mechanic will bear in mind that the file is a series of sharp, hard chisels he will plainly see that there are good reasons for the following rules for the use of files. Files should, when not in use, be kept in a wooden rack or hung up on wooden pins. Keeping them in a drawer or on a bench where they are knocked against each other or against other tools injures them and shortens their term of usefulness. You would not think of keeping sharp chisels in such a place.
Never use a new file on rough cast iron without first removing the scale with an old, worn file. All castings have a hard scale on the surface caused by the chilling of the metal when it is run into the damp molds. This scale or casing is often very thin and may be easily removed by grinding or by using an old, partly worn file, whereas a new file would be ruined on it by having its thin sharp teeth broken off. When this scale is removed the cast iron is generally easily cut by a sharp file.
Never attempt to file hardened steel with a good file. No toolsmith can temper a cold chisel so that it will cut hardened steel. Remember that your file is a series of sharp, hard cold chisels. In filing narrow surfaces bear on very lightly because only a few of the teeth can have a bearing on the metal at the same time, and too much force will cause them to cut too deeply and they are apt to be broken off. On wide surfaces many teeth will be cutting at one time and it will be found necessary to bear on quite hard in order to make the file take hold or bite. As a rule the whole length of the file should be used at each stroke. In order to do this it is necessary that the file be provided with a handle. For this purpose nothing is better than a good wooden handle with a strong ferrule. The easiest way to fit a handle to a file is to have a hole a little too small to fit the tang. Then heat the tang of an old file of the same size as the new one and burn to a fit. The center line of the handle should be exactly parallel with the length of the file.
The teeth of the file are made to cut in but one direction, and the file should be lifted from the work on the back stroke. The proper height for heavy or medium work to be held for easiest filing is on a level with the workman's elbow. For light work (such as saw filing), it should be much higher. A file to do good work must be kept clean and free from filings which tend to fill the spaces between the teeth and thus hold the teeth out from the work and prevent the file from "taking hold" of the work freely. The filings from cast iron and brass may usually be brushed out with a stiff bristle brush; but those from wrought iron and steel often stick much tighter and must be removed by the use of a wire brush or card. Sometimes small particles of steel become packed firmly that the wire brush will not loosen them, and what is called scorer must be resorted to. A scorer is made by flattening out the end of a small rod or wire of soft iron and making a comb out of it by drawing it across the file lengthwise of the teeth.