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3. Filing and filing tools

Filing is the most widely used fitting operation in the practice of metalworking shops "used for cutting metal by means of a tool known as a file. By means of a file it is possible to give a different shape and size to a workpiece, to fit one part to another, etc.

The most widely used operations with a file are: (1) filing separate surfaces, (2) filing mating surfaces, (3) filing holes.

A file is a hardened steel bar having a great number of fine cutting edges or teeth running diagonally across its face. These teeth can remove fine chips from a treated workpiece. A file differs from a chisel in having a large number of cutting points instead of one cutting edge and in being driven directly by hand instead of by hammer.

There are various kinds of files applied for finishing different workpieces depending on the shape of their surfaces (Fig. 9).

Flat files are used for filing flat surfaces but the shape of the files is not quite flat because if the file had been made quite flat, it would have prevented the

production of a flat surface, as the file would have cut away at the edges of a work and would have left a convex surface.

For filing convex and concave surfaces half-round files are used. A half-round file is made with a convex surface to prevent all the teeth from cutting at the same time, which requires too' much pressure on the file, as well as to prevent the file from bending.

Square files are applied for filing square holes and rectangle grooves, while triangular or three-square files are used for filing angles.

Round files are used for filing round holes of small diameters, and for filing metal in narrow plates diamond shaped files made of copper strip into which diamond powder has been hammered, or knife files are used.

For filing soft metals rasp files or rasps are employed.

Exercises

I. Use the following words and phrases in sentences of your own:

to file, to fit, mating surfaces, face, a great number of, convex surfaces, triangular file, to prevent, strip

II. Retell the text giving answers to the following questions.

1. What is filing? 2. What tools are used for filing operations? 3. What operations are performed with a file? 4. What is the difference between a file and a chisel? 5. How is cutting performed with a file? 6. What files are used for filing depending on the shape of the surfaces to be finished?

knife file

rhombic file, diamond-shaped file

round file

triangular file

square file

half round file

flat file

Fig.9. Files

a- edge; b- face; c- handle

III. Supply antonyms for the following words:

flat, convex, soft, different

IV. Give the derivatives from the following words and translate them into Russian:

to differ, to operate, file, to fit, diagonal, to finish, to separate

V. Change the following sentences using the subordinate clauses instead of participle phrases and translate the sentences into Russian:

Example: Files with convex surfaces, preventing all their teeth from cutting at the same time, are used for filing convex and concave surfaces. Files with convex surfaces which prevent all their teeth from cutting at the same time are used for filing convex and concave surfaces.

1. Files are generally made with convex surfaces being thicker in the middle than at the ends. 2. Files having various shapes of cross-section such as square, flat, round, etc. are used in metal-cutting practice. 3. When filing convex surfaces one uses a half-round file. 4. A file is an instrument having teeth on its face. 5. Files are tools belonging to the group of locksmith's cutting instruments. 6. Files having single cut teeth are called "single-cut files". 7. For removing a large amount of metal one uses a coarse-pitched file.

VI. Make up questions to which the italicized words are the answers:

1. A file has a great number of fine cutting teeth. 2. These teeth are used for removing chips from the workpiece to be treated. 3. Depending on the shape of the surfaces to be filed various kinds of files are used. 4. No, flat files are not used for filing round holes. Round files are used. 5. No, knife files are not used for filing soft metals, but rasps are used. 6. Yes, diamond-shaped files are used for filing metal in narrow, places.

VII. Giving answers to the following quest ions describe Fig. 9:

1. What is a file? 2. What principal parts does a file consist of? 3. In what cases is a square file used? 4. Which file is used for filing angles'? 5. What material are diamond-shaped files made of? 6. In what cases are knife files used?