Figure 1-20.—File information

Grades Files are graded according to the degree of fineness and whether they have single- or double-cut teeth. The difference is apparent when you compare the files in figure 1-20, view A. Single-cut files have rows of teeth cut parallel to each other. These teeth are set at an angle of about 65 degrees with the centerline. You will use single-cut files for sharpening tools, finish filing, and drawfiling. They are also the best tools for smoothing the edges of sheet metal. Files with crisscrossed rows of teeth are double-cut files. The double cut forms teeth that are diamond-shaped and fast cutting. You will use double-cut files for quick removal of metal and for rough work. Files are also graded according to the spacing and size of their teeth, or their coarseness and fineness. Some of these grades are pictured in view B. In addition to the three grades shown, you may use some DEAD SMOOTH files, which have very fine teeth, and some ROUGH files, with very coarse teeth. The fineness or coarseness of file teeth is also influenced by the length of the file. (The length of a file is the distance from the tip to the heel, and does not include the tang view C.) When you have a chance, compare the actual size of the teeth of a 6-inch, single-cut smooth file and a 12-inch, single-cut smooth file; you will notice the 6-inch file has more teeth per inch than the 12-inch file. Shapes Files come in different shapes. Therefore, in selecting a file for a job, consider the shape of the finished work. Some of the cross-sectional shapes are shown in figure 1-20, view D. TRIANGULAR files are tapered on all three sides. They are used to file acute internal angles and to clear out square corners. Special triangular files are used to file saw teeth. MILL files are tapered in both width and thickness. One edge has no teeth and is known as a SAFE EDGE. Mill files are used for smoothing lathe work, drawfiling, and other fine, precision work. Mill files are always single-cut. FLAT files are general-purpose files and may be either single- or double-cut. They are tapered in width and thickness. HARD files, not shown, are somewhat thicker than flat files. They taper slightly in thickness, but their edges are parallel. The flat or hard files most often used are the double-cut for rough work and the single-cut smooth file for finish work. 1-14 Figure 1-20.—File information.