Tests carried out have revealed that the work done by a file varies according to the character of the metal on which it is employed, according to the amount of pressure exerted for each cut, and to the cut of the teeth. It will thus be seen that it is bad practice, though it is quite frequently done, to use one file for all sorts of metals. In good filing files of different kinds should be selected with an eye to the resistance offered by the metal which which has to be filed. Other factors which affect the output of a file are the heating of the metal being filed. This may increase the weight of metal removed ; the breaking of the point of the teeth, which lowers the output; and, finally, accidental oiling of the work, which also lessens the amount of metal removed.

The efficiency and economy of files depend largely upon the organisation of the establishment which uses them. No other tools have so many varieties of shape and cuts to suit varying needs. In spite of this, it frequently happens that firms, either because their workmen are conservative, or because they do not know that special files have been invented to meet their special needs, continue to order ordinary files for work which needs a particular file. This practice should be discouraged, first, for the sake of the file, second, for the sake of the work it is intended to do, and finally for the sake of the file-maker.

The ordinary file cannot give such effective service for special work as the file which has been designed for that work alone. Consequently the work will not be so well done ; the file itself, being improperly used, will wear out much quicker ; and this will give the impression that the maker's files are bad files, when in reality this is by no means the case. It is in the interests of all parties that the buyer should understand something about files, and realise that there is a correct file for every class of work. If he is in doubt what kind of file to order, a word to the filemaker giving the purpose the file is to be used for will be a safeguard.

In a good workshop the workman knows that he is able to get the exact file he requires, and has then no excuse for using one file to do the work of another.

Files are supplied, broadly speaking, in four different cuts, namely : bastard, second-cut, smooth, and dead smooth. There are also rough and middle cuts, less frequently used.

(Edgar Allen and Co., Lid.)

The composition of steel for files may be as follows :-

Carbon........ ;1-2 to 1-5%

Silicon ........ ;-1 ,, -3%

Manganese .... ;-3 ,, -6%

Sulphur not over ;05%

Phosphorus „ ;05%

Small, also smooth cut files from the higher carbon steel, and larger ones, say 12in. and upwards, from the lower carbon steel.

(The Engineer.)