In draw-filing, take short, quick strokes, which will prevent the file from pinning and scratching. Long strokes, no matter how long the work may be, are useless save to make scratches. Remember that it is less the number of strokes you give the file than the weight you place upon it that is effective; therefore, when using a rough file, stand sufficiently away from the vise to bring the weight of the body upon the forward stroke. New files should be used at first upon broad surfaces, since narrow edges are apt to break the teeth if they have the fibrous edges unworn. For brass-work, use the file on a broad surface until its teeth are dulled, then make two or three strokes of the file under a heavy pressure upon the edge of a piece of sheet-iron, which will break off the dulled edges of the teeth, and leave a new fibrous edge for the brass-work. Use bastard-cut files to take off a quantity of metal of ordinary hardness; second-cut, in fitting, and also to file unusually hard metal; smoothing, to finish in final adjustment or preparatory to applying emery-cloth; dead smooth, to finish very fine work; float-file on lathe-work.

How To Prevent Scratching By Files

To prevent files from pinning, and hence from scratching, properly clean them, and then chalk them well.

How To Resharpen Files

(1) Carefully clean them with hot water and soda, then place them in connection with the positive pole of a battery in a bath composed of 4 parts of sulphuric acid and 100 parts water. The negative pole is to be formed of a copper spiral, surrounding the files but not touching them; the coil terminates in a wire reaching above the surface. Leave the files in the bath ten minutes, then carefully wash them off, dry, and oil. (2) Carefully clean the files in hot water and soda, and dip for 40 minutes in nitric acid of 410 B.

How To Select Files

To choose a flat file, turn it edge upward, and look along it, selecting those that have an even sweep from end to end, and having no flat places or hollows. To choose a half-round file, turn the edge upward, look along it, and select that which has an even sweep, and no flat or hollow places on the half-round side, even though it be hollow in the length of the flat side.