File (tool)

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Detail of a double-cut flat file

A file (or hand-file) is a hand tool used to shape material by abrasion. A file typically takes the form of a hardened steel bar, mostly covered with a series of sharp, parallel ridges or teeth. Most files have a narrow, pointed tang at one end to which a handle can be fitted.

The rasp is a related tool which is generally larger and has raised, pointed teeth on its surface rather than straight ridges.

1 Classification
2 Use
3 Specialized file types
4 See also

[edit] Classification

Relative tooth sizes for smooth, 2nd cut and bastard files

Files come in a wide variety of sizes, shapes, and tooth configurations. The cross-section of a file can be flat, round, half-round, triangular, square, knife edge or of a more specialized shape. A file's teeth can range from rough, coarse and bastard (meaning intermediate) to second-cut, smooth and dead smooth. A single-cut or mill file has one set of parallel teeth, while a cross-cut or double-cut file has a second set at an angle to the first. In Swiss-pattern files the teeth are cut at a shallower angle. Most files have teeth on all faces, but some specialty flat files have teeth only on the face or only on the edge, so that the direction of cutting can be more carefully controlled.

[edit] Use

Files have forward-facing cutting teeth, which means that the file cuts effectively only when pushed over the workpiece. Pulling a file over a workpiece or scraping a file back and forth is ineffective and will reduce the life of the file.

The grooves in a file may became clogged during use, causing the file to lose its cutting ability. A file card can be used to clean the file.

Files should always be used with a handle, otherwise the naked tang can injure the operator.

[edit] Specialized file types

[edit] Diamond files

A selection of diamond impregnated files

Instead of having teeth cut into the file's working surface, diamond files (pictured to the right) have small particles of industrial diamonds embedded in their surface (or into a softer material that is bonded to the underlying surface of the file). The use of diamonds in this manner allows the file to be used effectively against extremely hard materials, materials that would blunt an ordinary high carbon steel file quickly.

[edit] Needle files

A selection of small needle files

The image to the left shows a selection of needle files in an assortment of cross sectional shapes.
Needle files are usually sold in sets of 6 or 12 (or more) different shapes, packaged in a soft pouch, both for ease of handling and protection of the files' teeth. They are small files that are used in applications where the surface finish takes priority over metal removal rates but they are most suited for smaller work pieces.
They are often used as pictured, however, like all files, they are safest when used with a handle. The handle is often designed around the collet principle which allows the files and handle to be interchanged quickly.

[edit] Riffler files

A selection of riffler files

Riffler files, as pictured to the right, are small to medium sized files in an assortment of cross sectional shapes and profiles. The varying profiles and shapes enable them to be used in hard to reach, or unusually shaped areas. They are often used as an intermediate step in die making where the surface finish of a cavity die may need to be improved. - eg; plastic injection moulding or die casting

[edit] Machine files

A selection of machine files

The files pictured on the left are designed for use in a filing machine.

A filing machine is similar in appearance to a scroll saw or band saw in that the file is mounted vertically in the middle of a table. When in operation the file reciprocates vertically while the workpiece is presented to the file's face and manipulated around the table/file as the shape requires.

The cone point of the pictured, top two files allows the files to center themselves firmly in the bottom file holder. The pictured, lower two files are required to be inserted into the bottom file holder and physically restrained with set screws, an identical process as for the top holder.

Filing machines are useful tools as they reduce fatigue and improve product accuracy, and although not usually seen in modern production environments, they may be found in older toolrooms or diemaking shops as an aid in the manufacture of specialist tooling.