COMMON HAND-TOOLS 269 



The length of a file is the distance from the heel H to the point 

 P (Fig. 130). The tang T is not included in the length. In order- 

 ing a file from the toolroom it is 

 necessary to state the length, the 

 degree of coarseness, and the shape. 



FIG. 130. Measuring a Jf . i 



j.1 tiie me 



For example, you may want a 14 s /\ r^\ 



in. flat bastard, or a 16 in. halfr 

 round float FIG. 129. Cross-Sections of 



Files. 



308. Methods of Filing. It requires a great deal of 

 practice to file a surface flat, as there is a great tendency for 

 the file "to rock or fulcrum" on the corners of the work and 

 make the surface rounding or crowning. The worker should 

 always take long strokes, not short 

 jerky ones. Figure 131 shows the 



correct method of holding a file. 

 asurng a 



one way a series of small grooves 



will be cut across the work. It is always best to drive the 

 file diagonally across the first direction to make a smoother 

 surface. If this is done the file will always bite (cut) better, 

 and as the marks can be seen the eye will tell when you have 

 filed over the whole surface. 



Sighting (looking) along the length of a new file will show 

 which side is the most "bellied" 

 (curved). This side is the best 

 one to use. 



Cast iron is harder to cut FIG. 131. Proper Method of 

 ., , C i A i i , Using a File, 



with a file than wrought iron or 



soft steel. A new file should never be used on rough cast 

 iron, as the scale will dull the teeth and soon spoil the file. 

 If the scale is not very deep it can be removed with the 

 cutting edge of a flat file. When a file is too dull for cast 



