Manufacture

Steel of the correct specification is sent in billets to the rolling mills, rolled to the required sizes, and cut to length. These lengths called " file-moods " are forged, tanged and pointed by small steam hammers, and are then termed " file blanks." These are then annealed, then smithed and straightened by hand before being ground. In the grinding a large grit-stone is generally used, the " skin" being ground away, and the surface made clear and the edges smoothed. It is then ready for cutting. File cutting, except for special cases, is now done by machinery, which machines strike very rapid blows of equal weight, the file blank being advanced after each blow, so that the cuts are equidistant. Hardening is the next operation for which the file is covered with a special secret preparation to protect the file teeth. Before the war of 1914 this preparation was made of a mixture of charcoal and flour. The file is then placed in a pot filled with molten lead, tang upward, so that the cut portion is immersed vertically in the lead. After a proper interval the file is taken out and hardened by immersion in a tank of salt water. Every file has to be hardened in this way, and one man can turn out 50 to 60 dozen average files per day. Considerable skill is required to prevent the files from warping when quenched. After hardening and tempering the files are taken to the scouring shop where they are held by tongs and moved back and forth over a fierce jet of steam and sand, that effectively cleans and scours them, they are then treated with a preparation in order that they may dry without rusting, and the tangs are dipped into molten lead to draw brittleness so as not to break in the handle and injure the user. Finally each file is tested by tapping lightly on a steel block to make sure that it contains no cracks, also inspected for shape and truth, then wrapped, labelled and packed.

Saw files are usually triangular in shape, or " three-square " to use the trade term, and are supplied in small sizes up to 12in. They are used for general saw work, such as filing the teeth of hand saws. Special kinds of saws have specially adapted files. For instance, there are band saw files, which are triangular with round edges; and mill saw files, used to file circular wood saws and mill webs (which are a special kind of saw for vertical machine-sawing). Topping files are supplied for the purpose of filing the tops of circular saws and mill webs. Pit saw files are for filing pit saws ; and finally, gullet-ing saw files are designed to deepen the teeth of saws with gullet teeth.

Cotter files should be used for filing key-ways. Warding files are specially designed for use in filing key wards, and there are also lock files, the purpose of which is conveyed in the name.

One could go on at some length recounting the many varieties of special files, but it is unnecessary to do so. Mention may, however, be made of block files, which are square in shape, and are bored to take a special handle for greater ease and efficiency in working. These files are used for cylinder work, valves, etc. Rail files are generally very rough cut-as low as 7 teeth per inch. They are used for hot work ; for instance, to remove the flange or " burr " which is found on a rail after it has been sawn. Rail files are supplied with either one or two tangs, and it depends upon the class of work whether a single or double-tanged file should be ordered. As a general indication, a double-tanged file should be used for prolonged and heavy work, and a single-tanged for all other. It is interesting to note that rail files can also be supplied with two round edges or one round edge, or with one round and one square edge, or even two square edges. The thickness of these files also varies according to the work, from 1/2 in. to 7/8 in.

Another useful point to be observed is that the average English file, if supplied by a good maker, should stand recutting two or three times. This cannot be done with American or Continental files, which are usually too light to be re-cut with safety. Although it does not pay to re-cut files in England, users abroad often find it possible to save a great amount of money in this way, steel being more difficult to obtain, and new files consequently dearer to buy.

An old file should be used first to clear away any slag before using a good file, then a bastard file should be used to take off the main bulk of the material to be filed. For instance, if a workman has to file away 1/16 in, of steel, he should certainly not begin the work with a smooth or dead smooth file. These take a smaller portion of the metal away with each stroke, owing to the smaller size of the teeth. A bastard file, however, files away the metal at a good speed, and the workman should continue to use this type until he is within a fraction of an inch of his finishing point.

A second-cut file is, for general work, by far the most useful file made. Its manner of preparation particularly favours all-round hand work. The first cut is made very fine; that is, with very small spaces between each stroke of the cutting tool. The second cut is struck in well, because the fineness of the first-cut gives it a good foundation. In consequence it has what workmen describe as a " sweeter " cut. After taking away the bulk of the material with a bastard file, and then using a second-cut file, it will be found that quite as much metal is removed by it without leaving the rough surface which is always seen when a bastard file alone has been used. In fact, in general work some men prefer to use a second-cut file for the whole job.