270 APPLIED SCIENCE 



iron, it may still be useful for cutting wrought iron or soft 

 steel. Some flat files have a safe edge, i.e., a smooth edge 

 with no teeth. Such files are used when it is necessary to 

 file out a corner, as the safe edge prevents cutting a groove 

 in one side of the corner when the other side is being filed. 

 Such a file is shown in Fig. 132. 



Files get clogged with chips and should be frequently 

 cleaned with a wire brush, called a file-card. This will 

 remove the chips, and keep the work from being scratched 

 and grooved. File-cards are generally carried 

 in the toolroom. When cutting cast iron 

 with a new file, a little white chalk should be 

 rubbed on the file; this chalk will absorb the 

 oil and the chips will not be so likely to stick. 

 Oil should never be used on a file for cast iron, 

 but will sometimes make a file work better 

 with Safe ~Ed^e on wrou S n t iron. It is, however, best not 

 to use oil if only one file is available for both 

 metals. When filing cast iron, the hand or finger should not 

 be rubbed over the work, as the work will become greasy 

 as a result and keep the file from cutting. 



When filing finished work in the vise, the lead or copper 

 jaws should always be used. Otherwise the vise jaw will 

 bite into the work. The work may be given a very smooth 

 finish by draw filing, which is simply drawing the file in a 

 direction at right angles to its length. A single-cut, second- 

 cut, or smooth file is best for draw filing. 



309. Use of Scrapers. When a job cannot be finished 

 accurately enough with a file, a tool called a scraper (Fig. 

 133) is used. Scrapers are generally made from octagonal 

 steel flattened on both ends and tempered very hard to a 



